Publications by authors named "Seongman Kim"

7 Publications

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Fascaplysin Sensitizes Anti-Cancer Effects of Drugs Targeting AKT and AMPK.

Molecules 2017 Dec 24;23(1). Epub 2017 Dec 24.

Department of Biomedical Chemistry, College of Biomedical & Health Science, Konkuk University, Chungju 27478, Chungbuk, Korea.

Fascaplysin, a natural product isolated from marine sponges, is a potential candidate for the development of anti-cancer drugs. However, the mechanism underlying its therapeutic effect of strengthening anti-cancer efficacy of other drugs is poorly understood. Here, we found that fascaplysin increases phosphorylation of protein kinase B (PKB), also known as AKT, and adenosine monophosphate-activated protein kinase (AMPK), which are considered therapeutic targets for cancer treatment due to their anti-apoptotic or pro-survival functions in cancer. A cell viability assay revealed that pharmacological suppression of AKT using LY294002 enhanced the anti-cancer effect of fascaplysin in various cancer cells. Similarly, fascaplysin was observed to have improved anti-cancer effects in combination with compound , a selective AMPK inhibitor. Another challenge showed that fascaplysin increased the efficacy of methotrexate (MTX)-mediated cancer therapy by suppressing genes related to folate and purine metabolism. Overall, these results suggest that fascaplysin may be useful for improving the anti-cancer efficacy of targeted anti-cancer drugs, such as inhibitors of phosphoinositide 3-kinase AKT signaling, and chemotherapeutic agents, such as MTX.
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http://dx.doi.org/10.3390/molecules23010042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5943942PMC
December 2017

Functional Characterization of the Serine-Rich Tract of Varicella-Zoster Virus IE62.

J Virol 2016 01 4;90(2):959-71. Epub 2015 Nov 4.

Department of Microbiology and Immunology, and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.

Unlabelled: The immediate early 62 protein (IE62) of varicella-zoster virus (VZV), a major viral trans-activator, initiates the virus life cycle and is a key component of pathogenesis. The IE62 possesses several domains essential for trans-activation, including an acidic trans-activation domain (TAD), a serine-rich tract (SRT), and binding domains for USF, TFIIB, and TATA box binding protein (TBP). Transient-transfection assays showed that the VZV IE62 lacking the SRT trans-activated the early VZV ORF61 promoter at only 16% of the level of the full-length IE62. When the SRT of IE62 was replaced with the SRT of equine herpesvirus 1 (EHV-1) IEP, its trans-activation activity was completely restored. Herpes simplex virus 1 (HSV-1) ICP4 that lacks a TAD very weakly (1.5-fold) trans-activated the ORF61 promoter. An IE62 TAD-ICP4 chimeric protein exhibited trans-activation ability (10.2-fold), indicating that the IE62 TAD functions with the SRT of HSV-1 ICP4 to trans-activate viral promoters. When the serine and acidic residues of the SRT were replaced with Ala, Leu, and Gly, trans-activation activities of the modified IE62 proteins IE62-SRTΔSe and IE62-SRTΔAc were reduced to 46% and 29% of wild-type activity, respectively. Bimolecular complementation assays showed that the TAD of IE62, EHV-1 IEP, and HSV-1 VP16 interacted with Mediator 25 in human melanoma MeWo cells. The SRT of IE62 interacted with the nucleolar-ribosomal protein EAP, which resulted in the formation of globular structures within the nucleus. These results suggest that the SRT plays an important role in VZV viral gene expression and replication.

Importance: The immediate early 62 protein (IE62) of varicella-zoster virus (VZV) is a major viral trans-activator and is essential for viral growth. Our data show that the serine-rich tract (SRT) of VZV IE62, which is well conserved within the alphaherpesviruses, is needed for trans-activation mediated by the acidic trans-activation domain (TAD). The TADs of IE62, EHV-1 IEP, and HSV-1 VP16 interacted with cellular Mediator 25 in bimolecular complementation assays. The interaction of the IE62 SRT with nucleolar-ribosomal protein EAP resulted in the formation of globular structures within the nucleus. Understanding the mechanisms by which the TAD and SRT of IE62 contribute to the function of this essential regulatory protein is important in understanding the gene program of this human pathogen.
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http://dx.doi.org/10.1128/JVI.02096-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4702665PMC
January 2016

The early UL31 gene of equine herpesvirus 1 encodes a single-stranded DNA-binding protein that has a nuclear localization signal sequence at the C-terminus.

Virology 2012 Oct 20;432(2):306-15. Epub 2012 Jun 20.

Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.

The amino acid sequence of the UL31 protein (UL31P) of equine herpesvirus 1 (EHV-1) has homology to that of the ICP8 of herpes simplex virus type 1 (HSV-1). Here we show that the UL31 gene is synergistically trans-activated by the IEP and the UL5P (EICP27). Detection of the UL31 RNA transcript and the UL31P in EHV-1-infected cells at 6h post-infection (hpi) as well as metabolic inhibition assays indicated that UL31 is an early gene. The UL31P preferentially bound to single-stranded DNA over double-stranded DNA in gel shift assays. Subcellular localization of the green fluorescent protein (GFP)-UL31 fusion proteins revealed that the C-terminal 32 amino acid residues of the UL31P are responsible for the nuclear localization. These findings may contribute to defining the role of the UL31P single-stranded DNA-binding protein in EHV-1 DNA replication.
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http://dx.doi.org/10.1016/j.virol.2012.05.031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3423489PMC
October 2012

Development of a bacterial artificial chromosome (BAC) recombineering procedure using galK-untranslated region (UTR) for the mutation of diploid genes.

J Virol Methods 2012 Jun 8;182(1-2):18-26. Epub 2012 Mar 8.

Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, United States.

Bacterial artificial chromosome (BAC) recombineering using galK selection allows DNA cloned in Escherichia coli to be modified without introducing an unwanted selectable marker at the modification site. Genomes of some herpesviruses have a pair of inverted repeat sequences that makes it very difficult to introduce mutations into diploid (duplicate) genes using the galK selection method. To mutate diploid genes, we developed a galK-UTR BAC recombineering procedure that blocks one copy of the target diploid gene by insertion of a galK untranslated region (UTR), which enables the simple mutation of the other copy. The blocked copy can then be replaced with an UTR-specific primer pair. The IR2 gene of equine herpesvirus 1 (EHV-1) maps within both the internal (IR) and terminal repeat (TR) of the genomic short region and is expressed at low levels because its promoter is TATA-less. Both IR2 promoters in EHV-1 BAC were replaced with a mutant IR2 promoter containing three Sp1-binding motifs and a consensus TATA box by galK-UTR BAC recombineering. The expression level of the IR2 protein controlled by the modified promoter increased approximately 4-fold as compared to that of wild-type EHV-1. The galK-UTR method will provide a useful tool in studies of herpesviruses.
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http://dx.doi.org/10.1016/j.jviromet.2012.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388943PMC
June 2012

Characterization of cis-acting elements required for autorepression of the equine herpesvirus 1 IE gene.

Virus Res 2012 Apr 14;165(1):52-60. Epub 2012 Jan 14.

Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.

The immediate-early protein (IEP), the major regulatory protein encoded by the IE gene of equine herpesvirus 1 (EHV-1), plays a crucial role as both transcription activator and repressor during a productive lytic infection. To investigate the mechanism by which the EHV-1 IEP inhibits its own promoter, IE promoter-luciferase reporter plasmids containing wild-type and mutant IEP-binding site (IEBS) were constructed and used for luciferase reporter assays. The IEP inhibited transcription from its own promoter in the presence of a consensus IEBS (5'-ATCGT-3') located near the transcription initiation site but did not inhibit when the consensus sequence was deleted. To determine whether the distance between the TATA box and the IEBS affects transcriptional repression, the IEBS was displaced from the original site by the insertion of synthetic DNA sequences. Luciferase reporter assays revealed that the IEP is able to repress its own promoter when the IEBS is located within 26-bp from the TATA box. We also found that the proper orientation and position of the IEBS were required for the repression by the IEP. Interestingly, the level of repression was significantly reduced when a consensus TATA sequence was deleted from the promoter region, indicating that the IEP efficiently inhibits its own promoter in a TATA box-dependent manner. Taken together, these results suggest that the EHV-1 IEP delicately modulates autoregulation of its gene through the consensus IEBS that is near the transcription initiation site and the TATA box.
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http://dx.doi.org/10.1016/j.virusres.2012.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388944PMC
April 2012

The early UL3 gene of equine herpesvirus-1 encodes a tegument protein not essential for replication or virulence in the mouse.

Virology 2011 Nov 13;420(1):20-31. Epub 2011 Sep 13.

Center for Molecular and Tumor Virology, Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA.

The UL3 gene of equine herpesvirus-1 (EHV-1) is retained in the genome of defective interfering particles and encodes a ~33kDa myristylated protein. Further characterization showed that the UL3 gene is trans-activated only by the sole immediate early (IE) protein and encodes an early protein that is dispensable for EHV-1 replication and localizes in the tegument of purified virions. UL3-deleted EHV-1 (vL11ΔUL3) exhibits properties of host cell tropism, plaque size, and growth kinetics similar to those of the parental virus. Expression levels of EHV-1 proteins representative of all three gene classes in vL11ΔUL3-infected cells were identical to those in cells infected with parental virus. Mice intranasally infected with vL11ΔUL3 and parental virus showed no significant difference in mortality or virus lung titers. These findings suggest that the UL3 protein does not play a major role in the biology of EHV-1 in cell culture or virulence in the mouse.
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http://dx.doi.org/10.1016/j.virol.2011.08.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3185175PMC
November 2011

Identification of functional domains of the IR2 protein of equine herpesvirus 1 required for inhibition of viral gene expression and replication.

Virology 2011 Sep 26;417(2):430-42. Epub 2011 Jul 26.

Department of Microbiology and Immunology, and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana LA 71130-3932, USA.

The equine herpesvirus 1 (EHV-1) negative regulatory IR2 protein (IR2P), an early 1,165-amino acid (aa) truncated form of the 1487-aa immediate-early protein (IEP), lacks the trans-activation domain essential for IEP activation functions but retains domains for binding DNA, TFIIB, and TBP and the nuclear localization signal. IR2P mutants of the N-terminal region which lack either DNA-binding activity or TFIIB-binding activity were unable to down-regulate EHV-1 promoters. In EHV-1-infected cells expressing full-length IR2P, transcription and protein expression of viral regulatory IE, early EICP0, IR4, and UL5, and late ETIF genes were dramatically inhibited. Viral DNA levels were reduced to 2.1% of control infected cells, but were vey weakly affected in cells that express the N-terminal 706 residues of IR2P. These results suggest that IR2P function requires the two N-terminal domains for binding DNA and TFIIB as well as the C-terminal residues 707 to 1116 containing the TBP-binding domain.
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http://dx.doi.org/10.1016/j.virol.2011.06.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388945PMC
September 2011