Publications by authors named "Eun-Young Erin Ahn"

19 Publications

  • Page 1 of 1

FAK in the nucleus prevents VSMC proliferation by promoting p27 and p21 expression via Skp2 degradation.

Cardiovasc Res 2021 Apr 11. Epub 2021 Apr 11.

Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, AL 36688.

Aim: Vascular smooth muscle cells (VSMCs) normally exhibit a very low proliferative rate. Vessel injury triggers VSMC proliferation, in part, through focal adhesion kinase (FAK) activation, which increases transcription of cyclin D1, a key activator for cell cycle-dependent kinases (CDKs). At the same time, we also observe that FAK regulates the expression of the CDK inhibitors (CDKIs) p27 and p21. However, the mechanism of how FAK controls CDKIs in cell cycle progression is not fully understood.

Methods And Results: We found that pharmacological and genetic FAK inhibition increased p27 and p21 by reducing stability of S-phase kinase-associated protein 2 (Skp2), which targets the CDKIs for degradation. FAK N-terminal domain interacts with Skp2 and an APC/C E3 ligase activator, fizzy-related 1 (Fzr1) in the nucleus, which promotes ubiquitination and degradation of both Skp2 and Fzr1. Notably, overexpression of cyclin D1 alone failed to promote proliferation of genetic FAK kinase-dead (KD) VSMCs, suggesting that the FAK-Skp2-CDKI signaling axis is distinct from the FAK-cyclin D1 pathway. However, overexpression of both cyclin D1 and Skp2 enables proliferation of FAK-KD VSMCs, implicating that FAK ought to control both activating and inhibitory switches for CDKs. In vivo, wire injury activates FAK in the cytosol and increased Skp2 and decreased p27 and p21 levels.

Conclusions: Both pharmacological FAK and genetic FAK inhibition reduced Skp2 expression in VSMCs upon injury, which significantly reduced intimal hyperplasia through elevated expression of p27 and p21. This study revealed that nuclear FAK-Skp2-CDKI signaling negatively regulates CDK activity in VSMC proliferation.

Translational Perspective: Increased VSMC proliferation contributes to pathological vessel narrowing in atherosclerosisand following vascular interventions. Blocking VSMC proliferation will reduce atherosclerosisprogression and increase patency of vascular interventions. We found that forced nuclear FAKlocalization by FAK inhibition reduced VSMC proliferation upon vessel injury. Nuclear FAKdecreased Skp2 protein expression by proteasomal degradation, thereby increasing theexpression of cell cycle inhibitors p27 and p21 and blocking cell cycle progression. This studyhas demonstrated the potential for FAK inhibitors in blocking VSMC proliferation to treat vessel narrowing diseases.
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http://dx.doi.org/10.1093/cvr/cvab132DOI Listing
April 2021

son is necessary for proper vertebrate blood development.

PLoS One 2021 25;16(2):e0247489. Epub 2021 Feb 25.

Department of Biological Sciences, California State University Chico, Chico, California, United States of America.

The gene SON is on human chromosome 21 (21q22.11) and is thought to be associated with hematopoietic disorders that accompany Down syndrome. Additionally, SON is an RNA splicing factor that plays a role in the transcription of leukemia-associated genes. Previously, we showed that mutations in SON cause malformations in human and zebrafish spines and brains during early embryonic development. To examine the role of SON in normal hematopoiesis, we reduced expression of the zebrafish homolog of SON in zebrafish at the single-cell developmental stage with specific morpholinos. In addition to the brain and spinal malformations we also observed abnormal blood cell levels upon son knockdown. We then investigated how blood production was altered when levels of son were reduced. Decreased levels of son resulted in lower amounts of red blood cells when visualized with lcr:GFP transgenic fish. There were also reduced thrombocytes seen with cd41:GFP fish, and myeloid cells when mpx:GFP fish were examined. We also observed a significant decrease in the quantity of T cells, visualized with lck:GFP fish. However, when we examined their hematopoietic stem and progenitor cells (HSPCs), we saw no difference in colony-forming capability. These studies indicate that son is essential for the proper differentiation of the innate and adaptive immune system, and further investigation determining the molecular pathways involved during blood development should elucidate important information about vertebrate HSPC generation, proliferation, and differentiation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247489PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7906411PMC
February 2021

Focal Adhesion Kinase Activity and Localization is Critical for TNF-α-Induced Nuclear Factor-κB Activation.

Inflammation 2021 Feb 2. Epub 2021 Feb 2.

Department of Biochemistry and Molecular Biology, University of South Alabama College of Medicine, 5851 N. USA Drive, Room 2366, Mobile, AL, 36688, USA.

While sustained nuclear factor-κB (NF-κB) activation is critical for proinflammatory molecule expression, regulators of NF-κB activity during chronic inflammation are not known. We investigated the role of focal adhesion kinase (FAK) on sustained NF-κB activation in tumor necrosis factor-α (TNF-α)-stimulated endothelial cells (ECs) both in vitro and in vivo. We found that FAK inhibition abolished TNF-α-mediated sustained NF-κB activity in ECs by disrupting formation of TNF-α receptor complex-I (TNFRC-I). Additionally, FAK inhibition diminished recruitment of receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and the inhibitor of NF-κB (IκB) kinase (IKK) complex to TNFRC-I, resulting in elevated stability of IκBα protein. In mice given TNF-α, pharmacological and genetic FAK inhibition blocked TNF-α-induced IKK-NF-κB activation in aortic ECs. Mechanistically, TNF-α activated and redistributed FAK from the nucleus to the cytoplasm, causing elevated IKK-NF-κB activation. On the other hand, FAK inhibition trapped FAK in the nucleus of ECs even upon TNF-α stimulation, leading to reduced IKK-NF-κB activity. Together, these findings support a potential use for FAK inhibitors in treating chronic inflammatory diseases.
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http://dx.doi.org/10.1007/s10753-020-01408-5DOI Listing
February 2021

SON inhibits megakaryocytic differentiation via repressing RUNX1 and the megakaryocytic gene expression program in acute megakaryoblastic leukemia.

Cancer Gene Ther 2020 Nov 27. Epub 2020 Nov 27.

Department of Pathology, Division of Molecular and Cellular Pathology, University of Alabama at Birmingham, Birmingham, AL, USA.

A high incidence of acute megakaryoblastic leukemia (AMKL) in Down syndrome patients implies that chromosome 21 genes have a pivotal role in AMKL development, but the functional contribution of individual genes remains elusive. Here, we report that SON, a chromosome 21-encoded DNA- and RNA-binding protein, inhibits megakaryocytic differentiation by suppressing RUNX1 and the megakaryocytic gene expression program. As megakaryocytic progenitors differentiate, SON expression is drastically reduced, with mature megakaryocytes having the lowest levels. In contrast, AMKL cells express an aberrantly high level of SON, and knockdown of SON induced the onset of megakaryocytic differentiation in AMKL cell lines. Genome-wide transcriptome analyses revealed that SON knockdown turns on the expression of pro-megakaryocytic genes while reducing erythroid gene expression. Mechanistically, SON represses RUNX1 expression by directly binding to the proximal promoter and two enhancer regions, the known +23 kb enhancer and the novel +139 kb enhancer, at the RUNX1 locus to suppress H3K4 methylation. In addition, SON represses the expression of the AP-1 complex subunits JUN, JUNB, and FOSB which are required for late megakaryocytic gene expression. Our findings define SON as a negative regulator of RUNX1 and megakaryocytic differentiation, implicating SON overexpression in impaired differentiation during AMKL development.
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http://dx.doi.org/10.1038/s41417-020-00262-9DOI Listing
November 2020

Targeting focal adhesion kinase in cancer cells and the tumor microenvironment.

Exp Mol Med 2020 06 9;52(6):877-886. Epub 2020 Jun 9.

Department of Biochemistry and Molecular Biology, University of South Alabama, College of Medicine, Mobile, AL, 36688, USA.

Focal adhesion kinase (FAK) is an integrin-associated protein tyrosine kinase that is frequently overexpressed in advanced human cancers. Recent studies have demonstrated that aside from FAK's catalytic activity in cancer cells, its cellular localization is also critical for regulating the transcription of chemokines that promote a favorable tumor microenvironment (TME) by suppressing destructive host immunity. In addition to the protumor roles of FAK in cancer cells, FAK activity within cells of the TME may also support tumor growth and metastasis through various mechanisms, including increased angiogenesis and vascular permeability and effects related to fibrosis in the stroma. Small molecule FAK inhibitors have demonstrated efficacy in alleviating tumor growth and metastasis, and some are currently in clinical development phases. However, several preclinical trials have shown increased benefits from dual therapies using FAK inhibitors in combination with other chemotherapies or with immune cell activators. This review will discuss the role of nuclear FAK as a driver for tumor cell survival as well as potential therapeutic strategies to target FAK in both tumors and the TME.
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http://dx.doi.org/10.1038/s12276-020-0447-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7338452PMC
June 2020

Hypoxia induces cancer cell-specific chromatin interactions and increases MALAT1 expression in breast cancer cells.

J Biol Chem 2019 07 5;294(29):11213-11224. Epub 2019 Jun 5.

Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama 36604

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long noncoding RNA overexpressed in various cancers that promotes cell growth and metastasis. Although hypoxia has been shown to up-regulate MALAT1, only hypoxia-inducible factors (HIFs) have been implicated in activation of the promoter in specific cell types and other molecular mechanisms associated with hypoxia-mediated MALAT1 up-regulation remain largely unknown. Here, we demonstrate that hypoxia induces cancer cell-specific chromatin-chromatin interactions between newly identified enhancer-like -regulatory elements present at the locus. We show that hypoxia-mediated up-regulation of MALAT1 as well as its antisense strand TALAM1 occurs in breast cancer cells, but not in nontumorigenic mammary epithelial cells. Our analyses on the genomic locus discovered three novel putative enhancers that are located upstream and downstream of the gene body. We found that parts of these putative enhancers are epigenetically modified to a more open chromatin state under hypoxia in breast cancer cells. Furthermore, our chromosome conformation capture experiment demonstrated that noncancerous cells and breast cancer cells exhibit different interaction profiles under both normoxia and hypoxia, and only breast cancer cells gain specific chromatin interactions under hypoxia. Although the HIF-2α protein can enhance the interaction between the promoter and the putative 3' enhancer, the gain of chromatin interactions associated with other upstream elements, such as putative -7 and -20 kb enhancers, were HIF-independent events. Collectively, our study demonstrates that cancer cell-specific chromatin-chromatin interactions are formed at the locus under hypoxia, implicating a novel mechanism of MALAT1 regulation in cancer.
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http://dx.doi.org/10.1074/jbc.RA118.006889DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6643033PMC
July 2019

FAK and Pyk2 activity promote TNF-α and IL-1β-mediated pro-inflammatory gene expression and vascular inflammation.

Sci Rep 2019 05 20;9(1):7617. Epub 2019 May 20.

Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, AL, 36688, USA.

Protein tyrosine kinase (PTK) activity has been implicated in pro-inflammatory gene expression following tumor necrosis factor-α (TNF-α) or interkeukin-1β (IL-1β) stimulation. However, the identity of responsible PTK(s) in cytokine signaling have not been elucidated. To evaluate which PTK is critical to promote the cytokine-induced inflammatory cell adhesion molecule (CAM) expression including VCAM-1, ICAM-1, and E-selectin in human aortic endothelial cells (HAoECs), we have tested pharmacological inhibitors of major PTKs: Src and the focal adhesion kinase (FAK) family kinases - FAK and proline-rich tyrosine kinase (Pyk2). We found that a dual inhibitor of FAK/Pyk2 (PF-271) most effectively reduced all three CAMs upon TNF-α or IL-1β stimulation compared to FAK or Src specific inhibitors (PF-228 or Dasatinib), which inhibited only VCAM-1 expression. In vitro inflammation assays showed PF-271 reduced monocyte attachment and transmigration on HAoECs. Furthermore, FAK/Pyk2 activity was not limited to CAM expression but was also required for expression of various pro-inflammatory molecules including MCP-1 and IP-10. Both TNF-α and IL-1β signaling requires FAK/Pyk2 activity to activate ERK and JNK MAPKs leading to inflammatory gene expression. Knockdown of either FAK or Pyk2 reduced TNF-α-stimulated ERK and JNK activation and CAM expression, suggesting that activation of ERK or JNK is specific through FAK and Pyk2. Finally, FAK/Pyk2 activity is required for VCAM-1 expression and macrophage recruitment to the vessel wall in a carotid ligation model in ApoE-/- mice. Our findings define critical roles of FAK/Pyk2 in mediating inflammatory cytokine signaling and implicate FAK/Pyk2 inhibitors as potential therapeutic agents to treat vascular inflammatory disease such as atherosclerosis.
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http://dx.doi.org/10.1038/s41598-019-44098-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527705PMC
May 2019

Nuclear Focal Adhesion Kinase Controls Vascular Smooth Muscle Cell Proliferation and Neointimal Hyperplasia Through GATA4-Mediated Cyclin D1 Transcription.

Circ Res 2019 07 17;125(2):152-166. Epub 2019 May 17.

From the Department of Biochemistry and Molecular Biology (K.J., J.M.M., H.P., S.-J.K., Y.A.R.R., W.T.G., J.-S.K., E.-Y.E.A., S.-T.S.L.), University of South Alabama, College of Medicine, Mobile.

Rationale: Neointimal hyperplasia is characterized by excessive accumulation of vascular smooth muscle cells (SMCs) leading to occlusive disorders, such as atherosclerosis and stenosis. Blood vessel injury increases growth factor secretion and matrix synthesis, which promotes SMC proliferation and neointimal hyperplasia via FAK (focal adhesion kinase).

Objective: To understand the mechanism of FAK action in SMC proliferation and neointimal hyperplasia.

Methods And Results: Using combined pharmacological FAK catalytic inhibition (VS-4718) and SMC-specific FAK kinase-dead (Myh11-Cre-ER) mouse models, we report that FAK regulates SMC proliferation and neointimal hyperplasia in part by governing GATA4- (GATA-binding protein 4) cyclin D1 signaling. Inhibition of FAK catalytic activity facilitates FAK nuclear localization, which is required for proteasome-mediated GATA4 degradation in the cytoplasm. Chromatin immunoprecipitation identified GATA4 binding to the mouse cyclin D1 promoter, and loss of GATA4-mediated cyclin D1 transcription diminished SMC proliferation. Stimulation with platelet-derived growth factor or serum activated FAK and redistributed FAK from the nucleus to cytoplasm, leading to concomitant increase in GATA4 protein and cyclin D1 expression. In a femoral artery wire injury model, increased neointimal hyperplasia was observed in parallel with elevated FAK activity, GATA4 and cyclin D1 expression following injury in control mice, but not in VS-4718-treated and SMC-specific FAK kinase-dead mice. Finally, lentiviral shGATA4 knockdown in the wire injury significantly reduced cyclin D1 expression, SMC proliferation, and neointimal hyperplasia compared with control mice.

Conclusions: Nuclear enrichment of FAK by inhibition of FAK catalytic activity during vessel injury blocks SMC proliferation and neointimal hyperplasia through regulation of GATA4-mediated cyclin D1 transcription.
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http://dx.doi.org/10.1161/CIRCRESAHA.118.314344DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6702425PMC
July 2019

SON haploinsufficiency causes impaired pre-mRNA splicing of CAKUT genes and heterogeneous renal phenotypes.

Kidney Int 2019 06 15;95(6):1494-1504. Epub 2019 Mar 15.

Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, USA; Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, Alabama, USA. Electronic address:

Although genetic testing is increasingly used in clinical nephrology, a large number of patients with congenital abnormalities of the kidney and urinary tract (CAKUT) remain undiagnosed with current gene panels. Therefore, careful curation of novel genetic findings is key to improving diagnostic yields. We recently described a novel intellectual disability syndrome caused by de novo heterozygous loss-of-function mutations in the gene encoding the splicing factor SON. Here, we show that many of these patients, including two previously unreported, exhibit a wide array of kidney abnormalities. Detailed phenotyping of 14 patients with SON haploinsufficiency identified kidney anomalies in 8 patients, including horseshoe kidney, unilateral renal hypoplasia, and renal cysts. Recurrent urinary tract infections, electrolyte disturbances, and hypertension were also observed in some patients. SON knockdown in kidney cell lines leads to abnormal pre-mRNA splicing, resulting in decreased expression of several established CAKUT genes. Furthermore, these molecular events were observed in patient-derived cells with SON haploinsufficiency. Taken together, our data suggest that the wide spectrum of phenotypes in patients with a pathogenic SON mutation is a consequence of impaired pre-mRNA splicing of several CAKUT genes. We propose that genetic testing panels designed to diagnose children with a kidney phenotype should include the SON gene.
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http://dx.doi.org/10.1016/j.kint.2019.01.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6534475PMC
June 2019

FAK inhibition reduces metastasis of α4 integrin-expressing melanoma to lymph nodes by targeting lymphatic VCAM-1 expression.

Biochem Biophys Res Commun 2019 02 17;509(4):1034-1040. Epub 2019 Jan 17.

Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, AL, 36688, United States. Electronic address:

Malignant melanoma typically metastasizes to lymph nodes (LNs) as a primary or in-transit lesion before secondary metastasis occurs, and LN biopsy is a common procedure to diagnose melanoma progression. Since cancer metastasis is a complex process where various interactions between tumor cells and the stroma play key roles in establishing metastatic lesions, the exact mechanisms underlying melanoma metastasis to LNs remains unknown. It has been known that focal adhesion kinase (FAK) activity promotes the expression of proinflammatory vascular cell adhesion molecule-1 (VCAM-1). As VCAM-1 is a major receptor for α4 integrin and plays a key role in leukocyte recruitment, we reasoned that inhibition of FAK activity may reduce VCAM-1 expression within LNs and thus reduce metastasis of α4 integrin-expressing melanoma to LNs. First, we found that a pharmacological FAK inhibitor, PF-271, blocked tumor necrosis factor-α (TNF-α)-mediated VCAM-1 expression on human dermal lymphatic endothelial cells (HDLECs). In vitro, PF-271 significantly decreased B16F10 melanoma adhesion to and transmigration through HDLECs compared to TNF-α treated cells. Furthermore, in vivo FAK inhibition by oral PF-271 administration reduced VCAM-1 expression in inguinal, cervical, and popliteal LNs compared to vehicle treated mice. Finally, in a footpad metastasis model, B16F10 melanoma cells were injected into the right footpad of C57BL/6 mice, and PF-271 (50 mg/kg, twice daily for 6 days) was orally administrated after 1 week of tumor transplantation. While untreated mice exhibited significant metastatic melanoma lesions in popliteal LNs, PF-271 treated mice showed only marginal melanoma metastasis. These results support the possibility that FAK inhibitors may be a novel preventative option in melanoma metastasis by blocking VCAM-1 expression in LNs.
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http://dx.doi.org/10.1016/j.bbrc.2019.01.050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6350924PMC
February 2019

Molecular Mechanism of Inhibition of Acid Ceramidase by Carmofur.

J Med Chem 2019 01 19;62(2):987-992. Epub 2018 Dec 19.

Department of Neurosurgery, Mitchell Cancer Institute , University of South Alabama , Mobile , Alabama 36617 United States.

Human acid ceramidase (AC) is a lysosomal cysteine amidase, which has received a great deal of interest in recent years as a potential target for the development of new therapeutics against melanoma and glioblastoma tumors. Despite the strong interest in obtaining structural information, only the structures of the apo-AC enzyme in its zymogen and activated conformations are available. In this work, the crystal structure of AC in complex with the covalent carmofur inhibitor is presented. Carmofur is an antineoplastic drug containing an electrophilic carbonyl reactive group that targets the catalytic cysteine. This novel structural data explains the basis of the AC inhibition, provides insights into the enzymatic properties of the protein, and is a great aid toward the structure-based drug design of potent inhibitors for AC, providing the detailed mechanism, which has eluded the scientific community for more than 30 years, of carmofur's mysterious 5-fluorouracil-independent antitumor activity.
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http://dx.doi.org/10.1021/acs.jmedchem.8b01723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863082PMC
January 2019

Irradiation of pediatric glioblastoma cells promotes radioresistance and enhances glioma malignancy genome-wide transcriptome changes.

Oncotarget 2018 Sep 25;9(75):34122-34131. Epub 2018 Sep 25.

Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA.

Pediatric glioblastoma (GBM) is a relatively rare brain tumor in children that has a dismal prognosis. Surgery followed by radiotherapy is the main treatment protocol used for older patients. The benefit of adjuvant chemotherapy is still limited due to a poor understanding of the underlying molecular and genetic changes that occur with irradiation of the tumor. In this study, we performed total RNA sequencing on an established stable radioresistant pediatric GBM cell line to identify mRNA expression changes following radiation. The expression of many genes was altered in the radioresistant pediatric GBM model. These genes have never before been reported to be associated with the development of radioresistant GBM. In addition to exhibiting an accelerated growth rate, radioresistant GBM cells also have overexpression of the DNA synthesis-rate-limiting enzyme ribonucleotide reductase, and pro-cathepsin B. These newly identified genes should be concertedly studied to better understand their role in pediatric GBM recurrence and progression after radiation. It was observed that the changes in multiple biological pathways protected GBM cells against radiation and transformed them to a more malignant form. These changes emphasize the importance of developing a treatment regimen that consists of a multiple-agent cocktail that acts on multiple implicated pathways to effectively target irradiated pediatric GBM. An alternative to radiation or a novel therapy that targets differentially expressed genes, such as metalloproteases, growth factors, and oncogenes and aim to minimize oncogenic changes following radiation is necessary to improve recurrent GBM survival.
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http://dx.doi.org/10.18632/oncotarget.26137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6183347PMC
September 2018

DNA Repair Molecular Beacon assay: a platform for real-time functional analysis of cellular DNA repair capacity.

Oncotarget 2018 Aug 3;9(60):31719-31743. Epub 2018 Aug 3.

University of South Alabama Mitchell Cancer Institute, Mobile, AL, USA.

Numerous studies have shown that select DNA repair enzyme activities impact response and/or toxicity of genotoxins, suggesting a requirement for enzyme functional analyses to bolster precision medicine or prevention. To address this need, we developed a DNA Repair Molecular Beacon (DRMB) platform that rapidly measures DNA repair enzyme activity in real-time. The DRMB assay is applicable for discovery of DNA repair enzyme inhibitors, for the quantification of enzyme rates and is sufficiently sensitive to differentiate cellular enzymatic activity that stems from variation in expression or effects of amino acid substitutions. We show activity measures of several different base excision repair (BER) enzymes, including proteins with tumor-identified point mutations, revealing lesion-, lesion-context- and cell-type-specific repair dependence; suggesting application for DNA repair capacity analysis of tumors. DRMB measurements using lysates from isogenic control and APE1-deficient human cells suggests the major mechanism of base lesion removal by most DNA glycosylases may be mono-functional base hydrolysis. In addition, development of a microbead-conjugated DRMB assay amenable to flow cytometric analysis further advances its application. Our studies establish an analytical platform capable of evaluating the enzyme activity of select DNA repair proteins in an effort to design and guide inhibitor development and precision cancer therapy options.
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http://dx.doi.org/10.18632/oncotarget.25859DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6114979PMC
August 2018

Identification of radiation responsive genes and transcriptome profiling via complete RNA sequencing in a stable radioresistant U87 glioblastoma model.

Oncotarget 2018 May 4;9(34):23532-23542. Epub 2018 May 4.

Department of Radiology, Medical College of Wisconsin, Milwaukee, WI, USA.

The absence of major progress in the treatment of glioblastoma (GBM) is partly attributable to our poor understanding of both GBM tumor biology and the acquirement of treatment resistance in recurrent GBMs. Recurrent GBMs are characterized by their resistance to radiation. In this study, we used an established stable U87 radioresistant GBM model and total RNA sequencing to shed light on global mRNA expression changes following irradiation. We identified many genes, the expressions of which were altered in our radioresistant GBM model, that have never before been reported to be associated with the development of radioresistant GBM and should be concertedly further investigated to understand their roles in radioresistance. These genes were enriched in various biological processes such as inflammatory response, cell migration, positive regulation of epithelial to mesenchymal transition, angiogenesis, apoptosis, positive regulation of T-cell migration, positive regulation of macrophage chemotaxis, T-cell antigen processing and presentation, and microglial cell activation involved in immune response genes. These findings furnish crucial information for elucidating the molecular mechanisms associated with radioresistance in GBM. Therapeutically, with the global alterations of multiple biological pathways observed in irradiated GBM cells, an effective GBM therapy may require a cocktail carrying multiple agents targeting multiple implicated pathways in order to have a chance at making a substantial impact on improving the overall GBM survival.
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http://dx.doi.org/10.18632/oncotarget.25247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5955095PMC
May 2018

miR-125b regulates differentiation and metabolic reprogramming of T cell acute lymphoblastic leukemia by directly targeting A20.

Oncotarget 2016 Nov;7(48):78667-78679

Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic malignancy. Although it has been reported that overexpression of miR-125b leads to T-ALL development, the underlying mechanisms of miR-125b action are still unclear. The goal of this study is to delineate the role of miR-125b in T-ALL development. We found that miR-125b is highly expressed in undifferentiated leukemic T cells (CD4-negative) while its expression is low in differentiated T cells (CD4-positive). Overexpression of miR-125b increased the CD4-negative population in T cells, whereas depletion of miR-125b by miR-125b-sponge decreased the CD4-negative cell population. We identified that A20 (TNFAIP3) is a direct target of miR-125b in T cells. Overexpression of miR-125b also increased glucose uptake and oxygen consumption in T cells through targeting A20. Furthermore, restoration of A20 in miR-125b-overexpressing cells decreased the CD4-negative population in T cell leukemia, and decreased glucose uptake and oxygen consumption to the basal level of T cells transfected with vector. In conclusion, our data demonstrate that miR-125b regulates differentiation and reprogramming of T cell glucose metabolism via targeting A20. Since both de-differentiation and dysregulated glucose metabolism contribute to the development of T-cell leukemia, these findings provide novel insights into the understanding and treatment of T-ALL.
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http://dx.doi.org/10.18632/oncotarget.12018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5346668PMC
November 2016

De Novo Mutations in SON Disrupt RNA Splicing of Genes Essential for Brain Development and Metabolism, Causing an Intellectual-Disability Syndrome.

Am J Hum Genet 2016 09 18;99(3):711-719. Epub 2016 Aug 18.

Division of Genetics, Department of Pediatrics, San Antonio Military Medical Center, Fort Sam Houston, TX 78234, USA; Department of Pediatrics, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.

The overall understanding of the molecular etiologies of intellectual disability (ID) and developmental delay (DD) is increasing as next-generation sequencing technologies identify genetic variants in individuals with such disorders. However, detailed analyses conclusively confirming these variants, as well as the underlying molecular mechanisms explaining the diseases, are often lacking. Here, we report on an ID syndrome caused by de novo heterozygous loss-of-function (LoF) mutations in SON. The syndrome is characterized by ID and/or DD, malformations of the cerebral cortex, epilepsy, vision problems, musculoskeletal abnormalities, and congenital malformations. Knockdown of son in zebrafish resulted in severe malformation of the spine, brain, and eyes. Importantly, analyses of RNA from affected individuals revealed that genes critical for neuronal migration and cortex organization (TUBG1, FLNA, PNKP, WDR62, PSMD3, and HDAC6) and metabolism (PCK2, PFKL, IDH2, ACY1, and ADA) are significantly downregulated because of the accumulation of mis-spliced transcripts resulting from erroneous SON-mediated RNA splicing. Our data highlight SON as a master regulator governing neurodevelopment and demonstrate the importance of SON-mediated RNA splicing in human development.
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http://dx.doi.org/10.1016/j.ajhg.2016.06.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5011044PMC
September 2016

SON and Its Alternatively Spliced Isoforms Control MLL Complex-Mediated H3K4me3 and Transcription of Leukemia-Associated Genes.

Mol Cell 2016 Mar;61(6):859-73

Mitchell Cancer Institute, University of South Alabama, Mobile, AL 36604, USA; Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, AL 36688, USA. Electronic address:

Dysregulation of MLL complex-mediated histone methylation plays a pivotal role in gene expression associated with diseases, but little is known about cellular factors modulating MLL complex activity. Here, we report that SON, previously known as an RNA splicing factor, controls MLL complex-mediated transcriptional initiation. SON binds to DNA near transcription start sites, interacts with menin, and inhibits MLL complex assembly, resulting in decreased H3K4me3 and transcriptional repression. Importantly, alternatively spliced short isoforms of SON are markedly upregulated in acute myeloid leukemia. The short isoforms compete with full-length SON for chromatin occupancy but lack the menin-binding ability, thereby antagonizing full-length SON function in transcriptional repression while not impairing full-length SON-mediated RNA splicing. Furthermore, overexpression of a short isoform of SON enhances replating potential of hematopoietic progenitors. Our findings define SON as a fine-tuner of the MLL-menin interaction and reveal short SON overexpression as a marker indicating aberrant transcriptional initiation in leukemia.
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http://dx.doi.org/10.1016/j.molcel.2016.02.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4799497PMC
March 2016

Transcript variants of RUNX1T1: new insight into t(8;21)-positive leukemia.

Leuk Res 2014 Sep 8;38(9):1018-9. Epub 2014 Jul 8.

Mitchell Cancer Institute, University of South Alabama, Mobile, AL 36604, USA; Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, AL 36688, USA. Electronic address:

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http://dx.doi.org/10.1016/j.leukres.2014.06.023DOI Listing
September 2014

New discoveries of old SON: a link between RNA splicing and cancer.

J Cell Biochem 2014 Feb;115(2):224-31

Mitchell Cancer Institute, University of South Alabama, Mobile, Alabama, 36604.

The SON protein is a ubiquitously expressed DNA- and RNA-binding protein primarily localized to nuclear speckles. Although several early studies implicated SON in DNA-binding, tumorigenesis and apoptosis, functional significance of this protein had not been recognized until recent studies discovered SON as a novel RNA splicing co-factor. During constitutive RNA splicing, SON ensures efficient intron removal from the transcripts containing suboptimal splice sites. Importantly, SON-mediated splicing is required for proper processing of selective transcripts related to cell cycle, microtubules, centrosome maintenance, and genome stability. Moreover, SON regulates alternative splicing of RNAs from the genes involved in apoptosis and epigenetic modification. In addition to the role in RNA splicing, SON has an ability to suppress transcriptional activation at certain promoter/enhancer DNA sequences. Considering the multiple SON target genes which are directly involved in cell proliferation, genome stability and chromatin modifications, SON is an emerging player in gene regulation during cancer development and progression. Here, we summarize available information from several early studies on SON, and highlight recent discoveries describing molecular mechanisms of SON-mediated gene regulation. We propose that our future effort on better understanding of diverse SON functions would reveal novel targets for cancer therapy.
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http://dx.doi.org/10.1002/jcb.24672DOI Listing
February 2014