Kwanghyun Lee

Molecular mechanism of Jmjd3‐mediated interleukin‐6 gene regulation in endothelial cells underlying spinal cord injury

J. Neurochem. (2012) 122, 272–282.

Regulation of DU145 prostate cancer cell growth by Scm-like with four mbt domains 2

Mammalian SFMBTs have been considered to be polycomb group repressors. However, molecular mechanisms underlying mammalian SFMBTs-mediated gene regulation and their biological function have not been characterized. In the present study, we identified YY1 and methylated histones as interacting proteins of human SFMBT2. We also found that human SFMBT2 binds preferentially to methylated histone H3 and H4 that are associated with transcriptional repression. Using DU145 prostate cancer cells as a model, we showed that SFMBT2 has a transcriptional repression activity on HOXB13 gene expression. In addition, occupancy of SFMBT2 coincided with enrichment of di- and tri-methylated H3K9 and H4K20 as well as tri-methylated H3K27 at the HOXB13 gene promoter. When SFMBT2 was depleted by siRNA in DU145 prostate cancer cells, significant up-regulation of HOXB13 gene expression and decreased cell growth were observed. Collectively, our findings indicate that human SFMBT2 may regulate cell growth via epigenetic regulation of HOXB13 gene expression in DU145 prostate cancer cells.

Cyclo(phenylalanine-proline) induces DNA damage in mammalian cells via reactive oxygen species

Cyclo(phenylalanine‐proline) is produced by various organisms such as animals, plants, bacteria and fungi. It has diverse biological functions including anti‐fungal activity, anti‐bacterial activity and molecular signalling. However, a few studies have demonstrated the effect of cyclo(phenylalanine‐proline) on the mammalian cellular processes, such as cell growth and apoptosis. In this study, we investigated whether cyclo(phenylalanine‐proline) affects cellular responses associated with DNA damage in mammalian cells. We found that treatment of 1 mM cyclo(phenylalanine‐proline) induces phosphorylation of H2AX (S139) through ATM‐CHK2 activation as well as DNA double strand breaks. Gene expression analysis revealed that a subset of genes related to regulation of reactive oxygen species (ROS) scavenging and production is suppressed by the cyclo(phenylalanine‐proline) treatment. We also found that cyclo(phenylalanine‐proline) treatment induces perturbation of the mitochondrial membrane, resulting in increased ROS, especially superoxide, production. Collectively, our study suggests that cyclo(phenylalanine‐proline) treatment induces DNA damage via elevation of ROS in mammalian cells. Our findings may help explain the mechanism underlying the bacterial infection‐induced activation of DNA damage response in host mammalian cells.

Identification of Novel OCT4 Genetic Variant Associated with the Risk of Chronic Hepatitis B in a Korean Population

Hepatitis B viral infection is a serious risk factor for chronic hepatitis B (CHB), cirrhosis and hepatocellular carcinoma. Recently, several genome‐wide association studies (GWASs) have been conducted to identify important genetic variant associated with the risk of CHB. In our previous GWAS, TCF19 was identified as one of the susceptibility genes for CHB risk (P=4.2×10−9 at rs1419881). In order to discover possible additional causal variants around TCF19, we performed an association study by genotyping single nucleotide polymorphisms (SNPs) in OCT4, a nearby gene to TCF19.

Role of type II protein arginine methyltransferase 5 in the regulation of Circadian Per1 gene.

Circadian clocks are the endogenous oscillators that regulate rhythmic physiological and behavioral changes to correspond to daily light-dark cycles. Molecular dissections have revealed that transcriptional feedback loops of the circadian clock genes drive the molecular oscillation, in which PER/CRY complexes inhibit the transcriptional activity of the CLOCK/BMAL1 heterodimer to constitute a negative feedback loop. In this study, we identified the type II protein arginine methyltransferase 5 (PRMT5) as an interacting molecule of CRY1. Although the Prmt5 gene was constitutively expressed, increased interaction of PRMT5 with CRY1 was observed when the Per1 gene was repressed both in synchronized mouse liver and NIH3T3 cells. Moreover, rhythmic recruitment of PRMT5 and CRY1 to the Per1 gene promoter was found to be associated with an increased level of histone H4R3 dimethylation and Per1 gene repression. Consistently, decreased histone H4R3 dimethylation and altered rhythmic Per1 gene expression were observed in Prmt5-depleted cells. Taken together, these findings provide an insight into the link between histone arginine methylation by PRMT5 and transcriptional regulation of the circadian Per1 gene.

SFMBT2 (Scm-like with four mbt domains 2) negatively regulates cell migration and invasion in prostate cancer cells

Metastatic prostate cancer is the leading cause of morbidity and mortality in men. In this study, we found that expression level of SFMBT2 is altered during prostate cancer progression and has been associated with the migration and invasion of prostate cancer cells. The expression level of SFMBT2 is high in poorly metastatic prostate cancer cells compared to highly metastatic prostate cancer cells. We also found that SFMBT2 knockdown elevates MMP-2, MMP-3, MMP-9, and MMP-26 expression, leading to increased cell migration and invasion in LNCaP and VCaP cells. SFMBT2 interacts with YY1, RNF2, N-CoR and HDAC1/3, as well as repressive histone marks such as H3K9me2, H4K20me2, and H2AK119Ub which are associated with transcriptional repression. In addition, SFMBT2 knockdown decreased KAI1 gene expression through up-regulation of N-CoR gene expression. Expression of SFMBT2 in prostate cancer was strongly associated with clinicopathological features. Patients having higher Gleason score (≥ 8) had substantially lower SFMBT2 expression than patients with lower Gleason score. Moreover, tail vein or intraprostatic injection of SFMBT2 knockdown LNCaP cells induced metastasis. Taken together, our findings suggest that regulation of SFMBT2 may provide a new therapeutic strategy to control prostate cancer metastasis as well as being a potential biomarker of metastatic prostate cancer.

Characterization of HDAC9 isoforms in brain microvessel bEnd.3 cells upon oxygen and glucose deprivation–reperfusion injury

Histone deacetylases (HDACs) and their inhibitors affect the integrity of blood–brain barrier (BBB) which plays an important role in pathological conditions of the central nervous system (CNS). In this study, expression of HDACs was examined in bEnd.3 endothelial cells subjected to oxygen and glucose deprivation (OGD)–reperfusion injury. Expression of histone deacetylase-related protein (HDRP) produced by alternative splicing of HDAC9 was found to increase significantly in bEnd.3 cells upon OGD–reperfusion injury. HDRP was primarily localized in the nucleus. To investigate potential target genes of HDRP, its transcript was depleted by RNA interference and gene expression was determined. We found that FAS and GADD45a gene expression was up-regulated in HDRP-depleted bEnd.3 cells subjected to OGD–reperfusion injury. Interestingly, these genes are known to be involved in apoptosis and permeability of vascular endothelial cells. Our study suggests that HDRP may play a significant role in BBB integrity after CNS damage.