Publications by authors named "Dongmin Kang"

67 Publications

A basic domain-derived tripeptide inhibits MITF activity by reducing its binding to promoter of target genes.

J Invest Dermatol 2021 Apr 3. Epub 2021 Apr 3.

Department of Anatomy and Cell Biology, School of Medicine, Kangwon National University, Chuncheon 24341, Republic of Korea. Electronic address:

The keratinocytes in ultraviolet (UV)-irradiated skin produce and secrete α-melanocyte-stimulating hormone (α-MSH). α-MSH upregulates the expression of microphthalmia-associated transcription factor (MITF) in melanocytes via the cyclic adenosine monophosphate/protein kinase A/cAMP response element-binding protein (cAMP/PKA/CREB) signaling pathway. Thereafter, MITF induces the expression of melanogenic genes, including the tyrosinase, tyrosinase related protein-1 (TYRP-1), and tyrosinase related protein-2 (TYRP-2) genes, which leads to the synthesis and accumulation of melanin. In this study, we examined whether MITF basic region-derived tripeptides can bind to DNA-binding domain of MITF and inhibit MITF-induced melanogenesis through the inhibition of MITF-DNA binding. MITF-KGR, a representative MITF-derived tripeptide, suppressed the transcriptional activity of MITF by disrupting its binding to the promoter region of the target genes, which resulted in the inhibition of skin epidermis thickness and melanin synthesis in vivo and in vitro. Our results indicate that MITF-KGR exerts an inhibitory effect on melanogenesis by targeting MITF.
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http://dx.doi.org/10.1016/j.jid.2021.01.037DOI Listing
April 2021

GV1001 interacts with androgen receptor to inhibit prostate cell proliferation in benign prostatic hyperplasia by regulating expression of molecules related to epithelial-mesenchymal transition.

Aging (Albany NY) 2021 02 4;13(3):3202-3217. Epub 2021 Feb 4.

Department of Anatomy, Seoul National University College of Medicine, Seoul, Republic of Korea.

Prostate cell proliferation, driven by testosterone, is a major characteristic of benign prostatic hyperplasia (BPH). GV1001, a human telomerase reverse transcriptase catalytic subunit, is an injectable formulation used as a cancer vaccine. It functions as a cell penetrating peptide to regulate cell proliferation. Here, we found that GV1001 effectively suppressed proliferation of prostatic stromal myofibroblasts (WPMY-1) and prostatic epithelial cells (RWPE-1 and WPE-NA22) treated with dihydrotestosterone. Also, GV1001 bound to androgen receptors (ARs) in the cytosol of stromal and epithelial cells. In an experimental animal model implanted with an infusion pump for spontaneous and continuous release of testosterone, revealed that GV1001 reduced prostatic hypertrophy and inhibited the cell proliferation and the expression of Ki67, proliferating cell nuclear antigen, and prostate specific antigen. In addition, GV1001 prevented fibrosis of the prostate by downregulating expression of prostatic epithelial-mesenchymal transition (EMT)-related proteins such as transforming growth factor (TGF)-β, Snail, Slug, N-cadherin, and Vimentin, and by up-regulating E-cadherin. Taken together, these results suggest that GV1001, which suppresses TGF-β-mediated EMT by outcompeting testosterone for binding to AR, is a potential therapeutic drug for BPH accompanied by prostatic fibrosis.
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http://dx.doi.org/10.18632/aging.202242DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7906190PMC
February 2021

Decoding the temporal nature of brain GR activity in the NFκB signal transition leading to depressive-like behavior.

Mol Psychiatry 2021 Jan 22. Epub 2021 Jan 22.

Seoul Centre, Korea Basic Science Institute, Seoul, South Korea.

The fine-tuning of neuroinflammation is crucial for brain homeostasis as well as its immune response. The transcription factor, nuclear factor-κ-B (NFκB) is a key inflammatory player that is antagonized via anti-inflammatory actions exerted by the glucocorticoid receptor (GR). However, technical limitations have restricted our understanding of how GR is involved in the dynamics of NFκB in vivo. In this study, we used an improved lentiviral-based reporter to elucidate the time course of NFκB and GR activities during behavioral changes from sickness to depression induced by a systemic lipopolysaccharide challenge. The trajectory of NFκB activity established a behavioral basis for the NFκB signal transition involved in three phases, sickness-early-phase, normal-middle-phase, and depressive-like-late-phase. The temporal shift in brain GR activity was differentially involved in the transition of NFκB signals during the normal and depressive-like phases. The middle-phase GR effectively inhibited NFκB in a glucocorticoid-dependent manner, but the late-phase GR had no inhibitory action. Furthermore, we revealed the cryptic role of basal GR activity in the early NFκB signal transition, as evidenced by the fact that blocking GR activity with RU486 led to early depressive-like episodes through the emergence of the brain NFκB activity. These results highlight the inhibitory action of GR on NFκB by the basal and activated hypothalamic-pituitary-adrenal (HPA)-axis during body-to-brain inflammatory spread, providing clues about molecular mechanisms underlying systemic inflammation caused by such as COVID-19 infection, leading to depression.
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http://dx.doi.org/10.1038/s41380-021-01016-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7821461PMC
January 2021

Diclofenac impairs autophagic flux via oxidative stress and lysosomal dysfunction: Implications for hepatotoxicity.

Redox Biol 2020 10 12;37:101751. Epub 2020 Oct 12.

College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea. Electronic address:

Treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with various side effects, including cardiovascular and hepatic disorders. Studies suggest that mitochondrial damage and oxidative stress are important mediators of toxicity, yet the underlying mechanisms are poorly understood. In this study, we identified that some NSAIDs, including diclofenac, inhibit autophagic flux in hepatocytes. Further detailed studies demonstrated that diclofenac induced a reactive oxygen species (ROS)-dependent increase in lysosomal pH, attenuated cathepsin activity and blocked autophagosome-lysosome fusion. The reactivation of lysosomal function by treatment with clioquinol or transfection with the transcription factor EB restored lysosomal pH and thus autophagic flux. The production of mitochondrial ROS is critical for this process since scavenging ROS reversed lysosomal dysfunction and activated autophagic flux. The compromised lysosomal activity induced by diclofenac also inhibited the fusion with and degradation of mitochondria by mitophagy. Diclofenac-induced cell death and hepatotoxicity were effectively protected by rapamycin. Thus, we demonstrated that diclofenac induces the intracellular ROS production and lysosomal dysfunction that lead to the suppression of autophagy. Impaired autophagy fails to maintain mitochondrial integrity and aggravates the cellular ROS burden, which leads to diclofenac-induced hepatotoxicity.
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http://dx.doi.org/10.1016/j.redox.2020.101751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7575798PMC
October 2020

CD99-PTPN12 Axis Suppresses Actin Cytoskeleton-Mediated Dimerization of Epidermal Growth Factor Receptor.

Cancers (Basel) 2020 Oct 9;12(10). Epub 2020 Oct 9.

Department of Anatomy and Cell Biology, School of Medicine, Kangwon National University, Chuncheon 24341, Korea.

The epidermal growth factor receptor (EGFR), a member of ErbB receptor tyrosine kinase (RTK) family, is activated through growth factor-induced reorganization of the actin cytoskeleton and subsequent dimerization. We herein explored the molecular mechanism underlying the suppression of ligand-induced EGFR dimerization by CD99 agonists and its relevance to tumor growth in vivo. Epidermal growth factor (EGF) activated the formation of c-Src/focal adhesion kinase (FAK)-mediated intracellular complex and subsequently induced RhoA-and Rac1-mediated actin remodeling, resulting in EGFR dimerization and endocytosis. In contrast, CD99 agonist facilitated FAK dephosphorylation through the HRAS/ERK/PTPN12 signaling pathway, leading to inhibition of actin cytoskeletal reorganization via inactivation of the RhoA and Rac1 signaling pathways. Moreover, CD99 agonist significantly suppressed tumor growth in a BALB/c mouse model injected with MDA-MB-231 human breast cancer cells. Taken together, these results indicate that CD99-derived agonist ligand inhibits epidermal growth factor (EGF)-induced EGFR dimerization through impairment of cytoskeletal reorganization by PTPN12-dependent c-Src/FAK inactivation, thereby suppressing breast cancer growth.
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http://dx.doi.org/10.3390/cancers12102895DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7599698PMC
October 2020

Quantitative and qualitative analysis of autophagy flux using imaging.

BMB Rep 2020 May;53(5):241-247

Department of Life Science, Fluorescence Core Imaging Center, Ewha Womans University, Seoul 03760, Korea.

As an intracellular degradation system, autophagy is an essential and defensive cellular program required for cell survival and cellular metabolic homeostasis in response to various stresses, such as nutrient deprivation and the accumulation of damaged organelles. In general, autophagy flux consists of four steps: (1) initiation (formation of phagophore), (2) maturation and completion of autophagosome, (3) fusion of autophagosomes with lysosomes (formation of autolysosome), and (4) degradation of intravesicular components within autolysosomes. The number of genes and reagents that modulate autophagy is increasing. Investigation of their effect on autophagy flux is critical to understanding the roles of autophagy in many physiological and pathological processes. In this review, we summarize and discuss ways to analyze autophagy flux quantitatively and qualitatively with the use of imaging tools. The suggested imaging method can help estimate whether each modulator is an inhibitor or a promoter of autophagy and elucidate the mode of action of specific genes and reagents on autophagy processes. [BMB Reports 2020; 53(5): 241-247].
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7262512PMC
May 2020

The Role of Hydrogen Peroxide and Peroxiredoxins throughout the Cell Cycle.

Antioxidants (Basel) 2020 Mar 26;9(4). Epub 2020 Mar 26.

Department of Life Science, Fluorescence Core Imaging Center, and Research Center for Cellular Homeostasis, Ewha Womans University, Seoul 03760, Korea.

Hydrogen peroxide (HO) is an oxidizing agent that induces cellular damage at inappropriate concentrations and gives rise to an arrest during cell cycle progression, causing cell death. Recent evidence indicates that HO also acts as a promoter for cell cycle progression by oxidizing specific thiol proteins. The intracellular concentration of HO is regulated tightly, enabling its use as a cellular signaling molecule while minimizing its potential to cause cellular damage. Peroxiredoxins (Prxs) have peroxidase activity toward HO, organic hydroperoxides, and peroxynitrite for protecting cells from oxidative stress. They are suggested to work as signaling mediators, allowing the local accumulation of HO by inactivating their peroxidase activity uniquely compared with other antioxidant proteins such as catalase and glutathione peroxidase. Given that Prxs are highly sensitive to oxidation by HO, they act as sensors and transducers of HO signaling via transferring their oxidation state to effector proteins. The concentrations of intracellular HO increase as the cell cycle progresses from G to mitosis. Here, we summarize the roles of Prxs with regard to the regulation of cell cycle-dependent kinase activity and anaphase-promoting complex/cyclosome in terms of changes in HO levels. Protection of the cell from unwanted progression of the cell cycle is suggested to be a role of Prx. We discuss the possible roles of Prxs to control HO levels.
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http://dx.doi.org/10.3390/antiox9040280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7222192PMC
March 2020

The impaired redox balance in peroxisomes of catalase knockout mice accelerates nonalcoholic fatty liver disease through endoplasmic reticulum stress.

Free Radic Biol Med 2020 02 23;148:22-32. Epub 2019 Dec 23.

Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea. Electronic address:

Peroxisomes are essential organelles for maintaining the homeostasis of lipids and reactive oxygen species (ROS). While oxidative stress-induced endoplasmic reticulum (ER) stress plays an important role in nonalcoholic fatty liver disease (NAFLD), the role of peroxisomes in ROS-mediated ER stress in the development of NAFLD remains elusive. We investigated whether an impaired peroxisomal redox state accelerates NAFLD by activating ER stress by inhibiting catalase, an antioxidant expressed exclusively in peroxisomes. Wild-type (WT) and catalase knockout (CKO) mice were fed either a normal diet or a high-fat diet (HFD) for 11 weeks. HFD-induced phenotype changes and liver injury accompanied by ER stress and peroxisomal dysfunction were accelerated in CKO mice compared to WT mice. Interestingly, these changes were also significantly increased in CKO mice fed a normal diet. Inhibition of catalase by 3-aminotriazole in hepatocytes resulted in the following effects: (i) increased peroxisomal HO levels as measured by a peroxisome-targeted HO probe (HyPer-P); (ii) elevated intracellular ROS; (iii) decreased peroxisomal biogenesis; (iv) activated ER stress; (v) induced lipogenic genes and neutral lipid accumulation; and (vi) suppressed insulin signaling cascade associated with JNK activation. N-acetylcysteine or 4-phenylbutyric acid effectively prevented those alterations. These results suggest that a redox imbalance in peroxisomes perturbs cellular metabolism through the activation of ER stress in the liver.
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http://dx.doi.org/10.1016/j.freeradbiomed.2019.12.025DOI Listing
February 2020

BAP1 promotes stalled fork restart and cell survival via INO80 in response to replication stress.

Biochem J 2019 10;476(20):3053-3066

Department of Life Science, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Korea.

The recovery from replication stress by restarting stalled forks to continue DNA synthesis is crucial for maintaining genome stability and thereby preventing diseases such as cancer. We previously showed that BRCA1-associated protein 1 (BAP1), a nuclear deubiquitinase with tumor suppressor activity, promotes replication fork progression by stabilizing the INO80 chromatin remodeler via deubiquitination and recruiting it to replication forks during normal DNA synthesis. However, whether BAP1 functions in DNA replication under stress conditions is unknown. Here, we show that BAP1 depletion reduces S-phase progression and DNA synthesis after treatment with hydroxyurea (HU). BAP1-depleted cells exhibit a defect in the restart of HU-induced stalled replication forks, which is recovered by the ectopic expression of INO80. Both BAP1 and INO80 bind chromatin at replication forks upon HU treatment. BAP1 depletion abrogates the binding of INO80 to replication forks and increases the formation of RAD51 foci following HU treatment. BAP1-depleted cells show hypersensitivity to HU treatment, which is rescued by INO80 expression. These results suggest that BAP1 promotes the restart of stress-induced stalled replication forks by recruiting INO80 to the stalled forks. This function of BAP1 in replication stress recovery may contribute to its ability to suppress genome instability and cancer development.
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http://dx.doi.org/10.1042/BCJ20190622DOI Listing
October 2019

Corrigendum to "Bispecific anti-mPDGFRβ x cotinine scFv-Cκ-scFv fusion protein and cotinine-duocarmycin can form antibody-drug conjugate-like complexes that exert cytotoxicity against mPDGFRβ expressing cells" [Methods 154 (2019) 125-135].

Methods 2019 Jul 15;164-165:122. Epub 2019 Jul 15.

Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 00380, Republic of Korea; Cancer Research Institute, Seoul National University College of Medicine, Seoul 00380, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul 00380, Republic of Korea. Electronic address:

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http://dx.doi.org/10.1016/j.ymeth.2019.07.011DOI Listing
July 2019

The flagellin-TLR5-Nox4 axis promotes the migration of smooth muscle cells in atherosclerosis.

Exp Mol Med 2019 07 10;51(7):1-13. Epub 2019 Jul 10.

Department of Life Science, Ewha Womans University, Seoul, Korea.

We hypothesized that NADPH oxidase 4 (Nox4) is involved in the formation of neointimal atherosclerotic plaques through the migration of smooth muscle cells (SMCs) in response to flagellin. Here, we demonstrate that TLR5-mediated Nox4 activation regulates the migration of SMCs, leading to neointimal plaque formation in atherosclerosis. To investigate the molecular mechanism by which the TLR5-Nox4 cascade mediates SMC migration, we analyzed the signaling cascade in primary vascular SMCs (VSMCs) from wild-type (WT) or Nox4 KO mice. Stimulation of VSMCs from Nox4 KO mice with flagellin failed to induce HO production and Rac activation compared with stimulation of VSMCs from WT mice. Moreover, the migration of Nox4-deficient VSMCs was attenuated in response to flagellin in transwell migration and wound healing assays. Finally, we performed partial carotid artery ligation in ApoE KO and Nox4ApoE DKO mice fed a high-fat diet (HFD) with or without recombinant FliC (rFliC) injection. Injection of rFliC into ApoE KO mice fed a HFD resulted in significantly increased SMC migration into the intimal layer, whereas SMC accumulation was not detected in Nox4ApoE DKO mice. We conclude that activation of the TLR5-Nox4 cascade plays an important role in the formation of neointimal atherosclerotic plaques.
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http://dx.doi.org/10.1038/s12276-019-0275-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6802658PMC
July 2019

Dehydrocostus lactone suppresses osteoclast differentiation by regulating NFATc1 and inhibits osteoclast activation through modulating migration and lysosome function.

FASEB J 2019 08 30;33(8):9685-9694. Epub 2019 May 30.

Department of Life Science, Ewha Womans University, Seoul, Republic of Korea.

Excessive osteoclast activity can lead to an imbalance between the synthesis and breakdown of bone, with pathologic consequences that include osteoporosis and periodontitis. Thus, controlling osteoclast differentiation and function has significant therapeutic implications. In this study, we investigated the effects of dehydrocostus lactone (DL) on osteoclast differentiation and activation and elucidated the possible mechanisms underlying these processes. DL suppressed osteoclast differentiation by reducing the expression of the nuclear factor of activated T-cells, cytoplasmic 1. When used to challenge differentiated osteoclasts, DL also effectively inhibited their enlargement and resorption activity, and biochemical approaches revealed that DL attenuates osteoclast activation by inhibiting the migration and lysosome biogenesis and secretion the down-regulation of integrin β, PKC-β, and autophagy related 5 expression. Furthermore, DL prevented bone destruction in inflammation- and ovariectomy-induced osteolytic mouse models. These results indicate that DL has therapeutic potential to treat bone diseases caused by excessive or hyperactive osteoclasts.-Lee, H. I., Lee, J., Hwang, D., Lee, G.-R., Kim, N., Kwon, M., Lee, H., Piao, D., Kim, H. J., Kim, N. Y., Kim, H. S., Seo, E. K., Kang, D., Jeong, W. Dehydrocostus lactone suppresses osteoclast differentiation by regulating NFATc1 and inhibits osteoclast activation through modulating migration and lysosome function.
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http://dx.doi.org/10.1096/fj.201900862RDOI Listing
August 2019

Absence of Cytosolic 2-Cys Prx Subtypes I and II Exacerbates TNF-α-Induced Apoptosis via Different Routes.

Cell Rep 2019 02;26(8):2194-2211.e6

Department of Life Science, Ewha Womans University, Seoul 03760, Korea; Research Center for Cell Homeostasis, Ewha Womans University, Seoul 03760, Korea. Electronic address:

There are abundant peroxiredoxin (Prx) enzymes, but an increase of cellular HO level always happens in apoptotic cells. Here, we show that cellular HO switches different apoptosis pathways depending on which type of Prx enzyme is absent. TNF-α-induced HO burst preferentially activates the DNA damage-dependent apoptosis pathway in the absence of PrxI. By contrast, the same HO burst stimulates the RIPK1-dependent apoptosis pathway in the absence of PrxII by inducing the destruction of cIAP1 in caveolar membrane. Specifically, HO induces the oxidation of Cys308 residue in the cIAP1-BIR3 domain, which induces the dimerization-dependent E3 ligase activation. Thus, the reduction in cIAP level by the absence of PrxII triggers cell-autonomous apoptosis in cancer cells and tumors. Such differential functions of PrxI and PrxII are mediated by interaction with H2AX and cIAP1, respectively. Collectively, this study reveals the distinct switch roles of 2-Cys Prx isoforms in apoptosis signaling.
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http://dx.doi.org/10.1016/j.celrep.2019.01.081DOI Listing
February 2019

Is stool frequency associated with the richness and community composition of gut microbiota?

Intest Res 2019 Jul 7;17(3):419-426. Epub 2019 Feb 7.

Department of Internal Medicine, Kosin University College of Medicine, Busan, Korea.

Background/aims: Recently, a number of studies have reported that the gut microbiota could contribute to human conditions, including obesity, inflammation, cancer development, and behavior. We hypothesized that the composition and distribution of gut microbiota are different according to stool frequency, and attempted to identify the association between gut microbiota and stool frequency.

Methods: We collected fecal samples from healthy individuals divided into 3 groups according to stool frequency: group 1, a small number of defecation (≤2 times/wk); group 2, normal defecation (1 time/day or 1 time/2 day); and group 3, a large number of defecation (≥2-3 times/day). We evaluated the composition and distribution of the gut microbiota in each group via 16S rRNA-based taxonomic profiling of the fecal samples.

Results: Fecal samples were collected from a total of 60 individuals (31 men and 29 women, aged 34.1±5.88 years), and each group comprised 20 individuals. The microbial richness of group 1 was significantly higher than that of group 3 and tended to decrease with increasing number of defecation (P<0.05). The biological community composition was fairly different according to the number of defecation, and Bacteroidetes to Firmicutes ratio was higher in group 1 than in the other groups. Moreover, we found specific strains at the family and genus levels in groups 1 and 3.

Conclusions: Bacteroidetes to Firmicutes ratio and the abundance of Bifidobacterium were different according to the stool frequency, and specific bacteria were identified in the subjects with large and small numbers of defecation, respectively. These findings suggest that stool frequency might be associated with the richness and community composition of the gut microbiota.
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http://dx.doi.org/10.5217/ir.2018.00149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6667361PMC
July 2019

Inactivation of the PtdIns(4)P phosphatase Sac1 at the Golgi by HO produced via Ca-dependent Duox in EGF-stimulated cells.

Free Radic Biol Med 2019 02 23;131:40-49. Epub 2018 Nov 23.

Department of Life Science, Ewha Womans University, Seoul 03760, Republic of Korea. Electronic address:

Binding of epidermal growth factor (EGF) to its cell surface receptor induces production of HO, which serves as an intracellular messenger. We have shown that exogenous HO reversibly inactivates the phosphatidylinositol 4-phosphate [PtdIns(4)P] phosphatase Sac1 (suppressor of actin 1) at the Golgi complex of mammalian cells by oxidizing its catalytic cysteine residue and thereby increases both the amount of Golgi PtdIns(4)P and the rate of protein secretion. Here we investigated the effects of EGF on Sac1 oxidation and PtdIns(4)P abundance at the Golgi in A431 cells. EGF induced a transient increase in Golgi PtdIns(4)P as well as a transient oxidation of Sac1 in a manner dependent on elevation of the intracellular Ca concentration and on HO. Oxidation of Sac1 occurred at the Golgi, as revealed with the use of the Golgi-confined Sac1-K2A mutant. Knockdown of Duox enzymes implicated these Ca-dependent members of the NADPH oxidase family as the major source of HO for Sac1 oxidation. Expression of a Golgi-targeted HO probe revealed transient EGF-induced HO production at this organelle. Our findings have thus uncovered a previously unrecognized EGF signaling pathway that links intracellular Ca mobilization to events at the Golgi including Duox activation, HO production, Sac1 oxidation, and PtdIns(4)P accumulation.
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http://dx.doi.org/10.1016/j.freeradbiomed.2018.11.021DOI Listing
February 2019

Accumulation of PtdIns(4)P at the Golgi mediated by reversible oxidation of the PtdIns(4)P phosphatase Sac1 by HO.

Free Radic Biol Med 2019 01 16;130:426-435. Epub 2018 Nov 16.

Yonsei Biomedical Research Institute, Yonsei University, Seoul 03722, Republic of Korea. Electronic address:

Phosphatidylinositol 4-phosphate [PtdIns(4)P] plays a key role in the biogenesis of transport vesicles at the Golgi complex by recruiting coat proteins and their accessory factors. The PtdIns(4)P content of the Golgi is determined by the concerted action of PtdIns 4-kinase (PI4K) and PtdIns(4)P phosphatase enzymes. Sac1 (suppressor of actin 1) is the major PtdIns(4)P phosphatase and is localized to the Golgi and endoplasmic reticulum. The targeting of both PI4Ks and Sac1 to the Golgi membrane is extensively regulated, as is the catalytic activity of PI4Ks at the Golgi. However, regulation of the catalytic activity of Sac1 has been largely unexplored. Here we show that Sac1undergoes reversible inactivation in mammalian cells when its catalytic Cys residue is oxidized by exogenous HO to form an intramolecular disulfide with Cys. The oxidative inactivation of Sac1 results in the accumulation of PtdIns(4)P at the Golgi, with this effect also being supported by the HO-induced activation of p38 mitogen-activated protein kinase (MAPK), which was previously shown to promote the translocation of Sac1 from the Golgi to the endoplasmic reticulum. The increase in Golgi PtdIns(4)P due to Sac1 inactivation, however, is faster than that due to Sac1 translocation. Exposure of cells to HO also increased membrane protein trafficking from the Golgi to the plasma membrane as well as protein secretion.
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http://dx.doi.org/10.1016/j.freeradbiomed.2018.11.008DOI Listing
January 2019

Improved dynamic monitoring of transcriptional activity during longitudinal analysis in the mouse brain.

Biol Open 2019 Jan 8;8(1). Epub 2019 Jan 8.

Western Seoul Center, Korea Basic Science Institute, Seoul 03759, South Korea

Bioluminescence imaging has proven to be a highly sensitive technique for assessing transcriptional activity toward understanding gene regulation patterns; however, application of this technique is limited for brain research. In particular, the poor spatiotemporal resolution is a major hurdle for monitoring the dynamic changes of transcriptional activity in specific regions of the brain during longitudinal analysis of living animals. To overcome this limitation, in this study, we modified a lentivirus-based luciferase glucocorticoid receptor (GR) reporter by inserting destabilizing sequence genes, and then the reporter was stereotaxically injected in the mouse infralimbic prefrontal cortex (IL-PFC). Using this strategy, we could successfully pin-point and monitor the dynamic changes in GR activity in IL-PFC during normal stress adaptation. The modified reporter showed a 1.5-fold increase in temporal resolution for monitoring GR activity compared to the control, with respect to the intra-individual coefficients of variation. This novel method has broad applications, as it is readily adaptable to different types of transcription factor arrays as well spanning wide target regions of the brain to other organs and tissues.
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http://dx.doi.org/10.1242/bio.037168DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6361206PMC
January 2019

Bispecific anti-mPDGFRβ x cotinine scFv-C-scFv fusion protein and cotinine-duocarmycin can form antibody-drug conjugate-like complexes that exert cytotoxicity against mPDGFRβ expressing cells.

Methods 2019 02 4;154:125-135. Epub 2018 Oct 4.

Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 00380, Republic of Korea; Cancer Research Institute, Seoul National University College of Medicine, Seoul 00380, Republic of Korea; Department of Biomedical Science, Seoul National University College of Medicine, Seoul 00380, Republic of Korea. Electronic address:

Antibody selection for antibody-drug conjugates (ADCs) has traditionally depended on its internalization into the target cell, although ADC efficacy also relies on recycling of the receptor-ADC complex, endo-lysosomal trafficking, and subsequent linker/antibody proteolysis. In this study, we observed that a bispecific anti-murine platelet-derived growth factor receptor beta (mPDGFRβ) x cotinine single-chain variable fragment (scFv)-kappa constant region (C)-scFv fusion protein and cotinine-duocarmycin can form an ADC-like complex to induce cytotoxicity against mPDGFRβ expressing cells. Multiple anti-mPDGFRβ antibody candidates can be produced in this bispecific scFv-C-scFv fusion protein format and tested for their ability to deliver cotinine-conjugated cytotoxic drugs, thus providing an improved approach for antibody selection in ADC development.
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http://dx.doi.org/10.1016/j.ymeth.2018.10.002DOI Listing
February 2019

The tyrosine kinase inhibitor imatinib mesylate suppresses uric acid crystal-induced acute gouty arthritis in mice.

PLoS One 2017 5;12(10):e0185704. Epub 2017 Oct 5.

Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.

Gouty arthritis is caused by the deposition of monosodium urate (MSU) crystals in joints. Despite many treatment options for gout, there is a substantial need for alternative treatments for patients unresponsive to current therapies. Tyrosine kinase inhibitors have demonstrated therapeutic benefit in experimental models of antibody-dependent arthritis and in rheumatoid arthritis in humans, but to date, the potential effects of such inhibitors on gouty arthritis has not been evaluated. Here we demonstrate that treatment with the tyrosine kinase inhibitor imatinib mesylate (imatinib) can suppress inflammation induced by injection of MSU crystals into subcutaneous air pouches or into the ankle joint of wild type mice. Moreover, imatinib treatment also largely abolished the lower levels of inflammation which developed in IL-1R1-/- or KitW-sh/W-sh mice, indicating that this drug can inhibit IL-1-independent pathways, as well as mast cell-independent pathways, contributing to pathology in this model. Imatinib treatment not only prevented ankle swelling and synovial inflammation when administered before MSU crystals but also diminished these features when administrated after the injection of MSU crystals, a therapeutic protocol more closely mimicking the clinical situation in which treatment occurs after the development of an acute gout flare. Finally, we also assessed the efficiency of local intra-articular injections of imatinib-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles in this model of acute gout. Treatment with low doses of this long-acting imatinib:PLGA formulation was able to reduce ankle swelling in a therapeutic protocol. Altogether, these results raise the possibility that tyrosine kinase inhibitors might have utility in the treatment of acute gout in humans.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185704PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628843PMC
October 2017

The Role of Peroxiredoxins in the Transduction of HO Signals.

Antioxid Redox Signal 2018 03 10;28(7):537-557. Epub 2017 Jul 10.

3 Department of Life Science, Ewha Womans University , Seoul, Korea.

Significance: Hydrogen peroxide (HO) is produced on stimulation of many cell surface receptors and serves as an intracellular messenger in the regulation of diverse physiological events, mostly by oxidizing cysteine residues of effector proteins. Mammalian cells express multiple HO-eliminating enzymes, including catalase, glutathione peroxidase (GPx), and peroxiredoxin (Prx). A conserved cysteine in Prx family members is the site of oxidation by HO. Peroxiredoxins possess a high-affinity binding site for HO that is lacking in catalase and GPx and which renders the catalytic cysteine highly susceptible to oxidation, with a rate constant several orders of magnitude greater than that for oxidation of cysteine in most HO effector proteins. Moreover, Prxs are abundant and present in all subcellular compartments. The cysteines of most HO effectors are therefore at a competitive disadvantage for reaction with HO. Recent Advances: Here we review intracellular sources of HO as well as HO target proteins classified according to biochemical and cellular function. We then highlight two strategies implemented by cells to overcome the kinetic disadvantage of most target proteins with regard to HO-mediated oxidation: transient inactivation of local Prx molecules via phosphorylation, and indirect oxidation of target cysteines via oxidized Prx. Critical Issues and Future Directions: Recent studies suggest that only a small fraction of the total pools of Prxs and HO effector proteins localized in specific subcellular compartments participates in HO signaling. Development of sensitive tools to selectively detect phosphorylated Prxs and oxidized effector proteins is needed to provide further insight into HO signaling. Antioxid. Redox Signal. 28, 537-557.
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http://dx.doi.org/10.1089/ars.2017.7167DOI Listing
March 2018

Self-Assembled Tb Complex Probe for Quantitative Analysis of ATP during Its Enzymatic Hydrolysis via Time-Resolved Luminescence in Vitro and in Vivo.

ACS Appl Mater Interfaces 2017 Jan 20;9(1):722-729. Epub 2016 Dec 20.

Department of Chemistry and Research Institute of Natural Sciences, Gyeongsang National University , Jinju, Korea.

To more accurately assess the pathways of biological systems, a probe is needed that may respond selectively to adenosine triphosphate (ATP) for both in vitro and in vivo detection modes. We have developed a luminescence probe that can provide real-time information on the extent of ATP, ADP, and AMP by virtue of the luminescence and luminescence lifetime observed from a supramolecular polymer based on a C symmetrical terpyridine complex with Tb (S1-Tb). The probe shows remarkable selective luminescence enhancement in the presence of ATP compared to other phosphate-displaying nucleotides including adenosine diphosphate (ADP), adenosine monophosphate (AMP), guanosine triphosphate (GTP), thymidine triphosphate (TTP), HPO (Pi), and pyrophosphate (PPi). In addition, the time-resolved luminescence lifetime and luminescence spectrum of S1-Tb could facilitate the quantitative measurement of the exact amount of ATP and similarly ADP and AMP within living cells. The time-resolved luminescence lifetime of S1-Tb could also be used to quantitatively monitor the amount of ATP, ADP, and AMP in vitro following the enzymatic hydrolysis of ATP. The long luminescence lifetime, which was observed into the millisecond range, makes this S1-Tb-based probe particularly attractive for monitoring biological ATP levels in vivo, because any short lifetime background fluorescence arising from the complex molecular environment may be easily eliminated.
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http://dx.doi.org/10.1021/acsami.6b12857DOI Listing
January 2017

Charge-transport model for conducting polymers.

Nat Mater 2017 02 14;16(2):252-257. Epub 2016 Nov 14.

Department of Applied Physics and Materials Science, California Institute of Technology, California 91125, USA.

The growing technological importance of conducting polymers makes the fundamental understanding of their charge transport extremely important for materials and process design. Various hopping and mobility edge transport mechanisms have been proposed, but their experimental verification is limited to poor conductors. Now that advanced organic and polymer semiconductors have shown high conductivity approaching that of metals, the transport mechanism should be discernible by modelling the transport like a semiconductor with a transport edge and a transport parameter s. Here we analyse the electrical conductivity and Seebeck coefficient together and determine that most polymers (except possibly PEDOT:tosylate) have s = 3 and thermally activated conductivity, whereas s = 1 and itinerant conductivity is typically found in crystalline semiconductors and metals. The different transport in polymers may result from the percolation of charge carriers from conducting ordered regions through poorly conducting disordered regions, consistent with what has been expected from structural studies.
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http://dx.doi.org/10.1038/nmat4784DOI Listing
February 2017

Complete genome sequence of bacteriophage P2559Y, a marine phage that infects Croceibacter atlanticus HTCC2559.

Mar Genomics 2016 Oct 7;29:35-38. Epub 2016 Jul 7.

Department of Biological Sciences, Inha University, Incheon 22212, Republic of Korea. Electronic address:

The genus Croceibacter of the family Flavobacteriaceae represents a ubiquitous component of marine bacterioplankton, and is known to be involved in the interaction with phytoplankton. Here, we report the isolation and genome sequencing of a lytic siphovirus P2559Y that infects Croceibacter atlanticus HTCC2559, the type strain of the genus Croceibacter. The complete genome of P2559Y was 43,153bp in length, with a GC content of 38.9%. Functional annotation of 51 genes predicted in the genome showed that the P2559Y genome had a modular architecture. Comparison to the genome of P2559S, another phage that infects the same host strain, revealed an interesting feature in the genetic diversity of phages infecting the genus Croceibacter. The two phage genomes had a synteny in the structure module and shared many structural genes, while little similarity was found in the DNA replication/metabolism module.
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http://dx.doi.org/10.1016/j.margen.2016.07.001DOI Listing
October 2016

Control of the pericentrosomal H2O2 level by peroxiredoxin I is critical for mitotic progression.

J Cell Biol 2015 Jul;210(1):23-33

Yonsei Biomedical Research Institute, Yonsei University, Seoul 120-749, South Korea

Proteins associated with the centrosome play key roles in mitotic progression in mammalian cells. The activity of Cdk1-opposing phosphatases at the centrosome must be inhibited during early mitosis to prevent premature dephosphorylation of Cdh1-an activator of the ubiquitin ligase anaphase-promoting complex/cyclosome-and the consequent premature degradation of mitotic activators. In this paper, we show that reversible oxidative inactivation of centrosome-bound protein phosphatases such as Cdc14B by H2O2 is likely responsible for this inhibition. The intracellular concentration of H2O2 increases as the cell cycle progresses. Whereas the centrosome is shielded from H2O2 through its association with the H2O2-eliminating enzyme peroxiredoxin I (PrxI) during interphase, the centrosome-associated PrxI is selectively inactivated through phosphorylation by Cdk1 during early mitosis, thereby exposing the centrosome to H2O2 and facilitating inactivation of centrosome-bound phosphatases. Dephosphorylation of PrxI by okadaic acid-sensitive phosphatases during late mitosis again shields the centrosome from H2O2 and thereby allows the reactivation of Cdk1-opposing phosphatases at the organelle.
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http://dx.doi.org/10.1083/jcb.201412068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4493999PMC
July 2015

Selective inhibition of the function of tyrosine-phosphorylated STAT3 with a phosphorylation site-specific intrabody.

Proc Natl Acad Sci U S A 2014 Apr 14;111(17):6269-74. Epub 2014 Apr 14.

Division of Life and Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, and Global Top 5 Research Program, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul 120-750, Korea.

Signal transducer and activator of transcription 3 (STAT3) is a multifunctional protein that participates in signaling pathways initiated by various growth factors and cytokines. It exists in multiple forms including those phosphorylated on Tyr(705) (pYSTAT3) or Ser(727) (pSSTAT3) as well as the unphosphorylated protein (USTAT3). In addition to the canonical transcriptional regulatory role of pYSTAT3, both USTAT3 and pSSTAT3 function as transcriptional regulators by binding to distinct promoter sites and play signaling roles in the cytosol or mitochondria. The roles of each STAT3 species in different biological processes have not been readily amenable to investigation, however. We have now prepared an intrabody that binds specifically and with high affinity to the tyrosine-phosphorylated site of pYSTAT3. Adenovirus-mediated expression of the intrabody in HepG2 cells as well as mouse liver blocked both the accumulation of pYSTAT3 in the nucleus and the production of acute phase response proteins induced by interleukin-6. Intrabody expression did not affect the overall accumulation of pSSTAT3 induced by interleukin-6 or phorbol 12-myristate 13-acetate (PMA), the PMA-induced expression of the c-Fos gene, or the PMA-induced accumulation of pSSTAT3 specifically in mitochondria. In addition, it had no effect on interleukin-6-induced expression of the gene for IFN regulatory factor 1, a downstream target of STAT1. Our results suggest that the engineered intrabody is able to block specifically the downstream effects of pYSTAT3 without influencing those of pSSTAT3, demonstrating the potential of intrabodies as tools to dissect the cellular functions of specific modified forms of proteins that exist as multiple species.
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http://dx.doi.org/10.1073/pnas.1316815111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4035943PMC
April 2014

Genome of a SAR116 bacteriophage shows the prevalence of this phage type in the oceans.

Proc Natl Acad Sci U S A 2013 Jul 24;110(30):12343-8. Epub 2013 Jun 24.

Division of Biology and Ocean Sciences, Inha University, Incheon 402-751, Korea.

The abundance, genetic diversity, and crucial ecological and evolutionary roles of marine phages have prompted a large number of metagenomic studies. However, obtaining a thorough understanding of marine phages has been hampered by the low number of phage isolates infecting major bacterial groups other than cyanophages and pelagiphages. Therefore, there is an urgent requirement for the isolation of phages that infect abundant marine bacterial groups. In this study, we isolated and characterized HMO-2011, a phage infecting a bacterium of the SAR116 clade, one of the most abundant marine bacterial lineages. HMO-2011, which infects "Candidatus Puniceispirillum marinum" strain IMCC1322, has an ~55-kb dsDNA genome that harbors many genes with novel features rarely found in cultured organisms, including genes encoding a DNA polymerase with a partial DnaJ central domain and an atypical methanesulfonate monooxygenase. Furthermore, homologs of nearly all HMO-2011 genes were predominantly found in marine metagenomes rather than cultured organisms, suggesting the novelty of HMO-2011 and the prevalence of this phage type in the oceans. A significant number of the viral metagenome sequences obtained from the ocean surface were best assigned to the HMO-2011 genome. The number of reads assigned to HMO-2011 accounted for 10.3%-25.3% of the total reads assigned to viruses in seven viromes from the Pacific and Indian Oceans, making the HMO-2011 genome the most or second-most frequently assigned viral genome. Given its ability to infect the abundant SAR116 clade and its widespread distribution, Puniceispirillum phage HMO-2011 could be an important resource for marine virus research.
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http://dx.doi.org/10.1073/pnas.1219930110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3725092PMC
July 2013

HBxAPα/Rsf-1-mediated HBx-hBubR1 interactions regulate the mitotic spindle checkpoint and chromosome instability.

Carcinogenesis 2013 Jul 27;34(7):1680-8. Epub 2013 Mar 27.

Department of Biochemistry and Molecular Biology, Ajou University School of Medicine and the Graduate School of Molecular Science and Technology, Ajou University, Suwon, South Korea.

Hepatitis B virus (HBV) X protein (HBx), encoded by the HBV genome, is involved in the development of HBV-mediated liver cancer, whose frequency is highly correlated with chromosomal instability (CIN). We reported previously that HBx induces mitotic checkpoint dysfunction by targeting the human serine/threonine kinase BubR1 (hBubR1). However, the underlying mechanism remained unresolved. Here, we show that HBx protein-associated protein α (HBxAPα)/Rsf-1 associates with hBubR1 and HBx in the chromatin fraction during mitosis. Depletion of HBxAPα/Rsf-1 abolished the interaction between HBx and hBubR1, indicating that HBxAPα/Rsf-1 mediates these interactions. Knockdown of HBxAPα/Rsf-1 with small interfering RNA did not affect the recruitment of hBubR1 to kinetochores; however, it did significantly impair HBx targeting to kinetochores. A deletion mutant analysis revealed that two Kunitz domains of HBx, the Cdc20-binding domain of hBubR1 and full-length of HBxAPα/Rsf-1 were essential for these interactions. Thus, binding of HBx to hBubR1, stabilized by HBxAPα/Rsf-1, significantly attenuated hBubR1 binding to Cdc20 and consequently increased the rate of mitotic aberrations. Collectively, our data show that the HBx impairs hBubR1 function and induces CIN through HBxAPα/Rsf-1, providing a novel mechanism for induction of genomic instability by a viral pathogen in hepatocarcinogenesis.
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http://dx.doi.org/10.1093/carcin/bgt105DOI Listing
July 2013

Sestrins activate Nrf2 by promoting p62-dependent autophagic degradation of Keap1 and prevent oxidative liver damage.

Cell Metab 2013 Jan 27;17(1):73-84. Epub 2012 Dec 27.

Division of Life and Pharmaceutical Sciences, Ewha Womans University, Seoul 120-750, Korea.

Sestrins (Sesns) protect cells from oxidative stress. The mechanism underlying the antioxidant effect of Sesns has remained unknown, however. The Nrf2-Keap1 pathway provides cellular defense against oxidative stress by controlling the expression of antioxidant enzymes. We now show that Sesn1 and Sesn2 interact with the Nrf2 suppressor Keap1, the autophagy substrate p62, and the ubiquitin ligase Rbx1 and that the antioxidant function of Sesns is mediated through activation of Nrf2 in a manner reliant on p62-dependent autophagic degradation of Keap1. Sesn2 was upregulated in the liver of mice subjected to fasting or subsequent refeeding with a high-carbohydrate, fat-free diet, whereas only refeeding promoted Keap1 degradation and Nrf2 activation, because only refeeding induced p62 expression. Ablation of Sesn2 blocked Keap1 degradation and Nrf2 activation induced by refeeding and thereby increased the susceptibility of the liver to oxidative damage resulting from the acute stimulation of lipogenesis associated with refeeding.
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http://dx.doi.org/10.1016/j.cmet.2012.12.002DOI Listing
January 2013

Coordinate synthesis but discrete localization of homologous N-glycosylated proteins, CLP and CLB, in Naegleria pringsheimi flagellates.

J Eukaryot Microbiol 2012 Nov-Dec;59(6):614-24. Epub 2012 Aug 13.

Department of Systems Biology, Yonsei University, Seoul, 120-749, Korea.

The synchronous amoebae-to-flagellates differentiation of Naegleria pringsheimi has been used as a model system to study the formation of eukaryotic flagella. We cloned two novel genes, Clp, Class I on plasma membrane and Clb, Class I at basal bodies, which are transiently expressed during differentiation and characterized their respective protein products. CLP (2,087 amino acids) and CLB (1,952 amino acids) have 82.9% identity in their amino acid sequences and are heavily N-glycosylated, leading to an ~ 100 × 10(3) increase in the relative molecular mass of the native proteins. In spite of these similarities, CLP and CLB were localized to distinct regions: CLP was present on the outer surface of the plasma membrane, whereas CLB was concentrated at a site where the basal bodies are assembled and remained associated with the basal bodies. Oryzalin, a microtubule toxin, inhibited the appearance of CLP on the plasma membrane, but had no effect on the concentration of CLB at its target site. These data suggest that N. pringsheimi uses separate mechanisms to transport CLP and CLB to the plasma membrane and to the site of basal body assembly, respectively.
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http://dx.doi.org/10.1111/j.1550-7408.2012.00642.xDOI Listing
April 2013

Complete genome sequence of Croceibacter bacteriophage P2559S.

J Virol 2012 Aug;86(16):8912-3

Division of Biology and Ocean Sciences, Inha University, Incheon, Republic of Korea.

Croceibacter atlanticus HTCC2559(T), a marine bacterium isolated from the Sargasso Sea, is a phylogenetically unique member of the family Flavobacteriaceae. Strain HTCC2559(T) possesses genes related to interaction with primary producers, which makes studies on bacteriophages infecting the strain interesting. Here we report the genome sequence of bacteriophage P2559S, which was isolated off the coast of the Republic of Korea and lytically infects HTCC2559(T). Many genes predicted in the P2559S genome had their homologs in Bacteroides phages.
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http://dx.doi.org/10.1128/JVI.01396-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3421703PMC
August 2012