Histone lysine methyltransferases (HKMTs) deposit methyl groups onto lysine residues on histones and play important roles in regulating chromatin structure and gene expression. The structures and functions of HKMTs have been extensively investigated in recent decades, significantly advancing our understanding of the dynamic regulation of histone methylation. Here, we review the recent progress in structural studies of representative HKMTs in complex with nucleosomes (H3K4, H3K27, H3K36, H3K79, and H4K20 methyltransferases), with emphasis on the molecular mechanisms of nucleosome recognition and trans-histone crosstalk by these HKMTs. These structural studies inform HKMTs' roles in tumorigenesis and provide the foundations for developing new therapeutic approaches targeting HKMTs in cancers.
Nucleosomes ; Histones/metabolism* ; Histone-Lysine N-Methyltransferase/metabolism* ; Lysine/metabolism* ; Methyltransferases/metabolism* ; Methylation

The histone methyltransferase enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2)-mediated trimethylation of histone H3 lysine 27 (H3K27me3) regulates neural stem cell proliferation and fate specificity through silencing different gene sets in the central nervous system. Here, we explored the function of EZH2 in early post-mitotic neurons by generating a neuron-specific Ezh2 conditional knockout mouse line. The results showed that a lack of neuronal EZH2 led to delayed neuronal migration, more complex dendritic arborization, and increased dendritic spine density. Transcriptome analysis revealed that neuronal EZH2-regulated genes are related to neuronal morphogenesis. In particular, the gene encoding p21-activated kinase 3 (Pak3) was identified as a target gene suppressed by EZH2 and H3K27me3, and expression of the dominant negative Pak3 reversed Ezh2 knockout-induced higher dendritic spine density. Finally, the lack of neuronal EZH2 resulted in impaired memory behaviors in adult mice. Our results demonstrated that neuronal EZH2 acts to control multiple steps of neuronal morphogenesis during development, and has long-lasting effects on cognitive function in adult mice.
Animals ; Mice ; Enhancer of Zeste Homolog 2 Protein/metabolism* ; Histone Methyltransferases/metabolism* ; Histones/genetics* ; Morphogenesis ; Neuronal Plasticity ; Neurons/metabolism*

OBJECTIVETo construct the eukaryotic expression plasmid of mouse histone lysine methyltransferase Setd7 and detect its effect on neuron development.

METHODSThe clone of mouse Setd7 was obtained and inserted into the eukaryotic expression vector pCMV-3tag-6-Flag. The plasmid was transfected into HEK 293T and identified by Western blot. Real-time PCR was used to detect the effect of Setd7 on the neuron differentiation marker gene Ngn 1 mRNA expression. Dual luciferase reporter system was used to detect the effect of Setd7 on Ngn 1 mRNA expression. Real-time PCR was used to detect the effect of Setd 7 siRNA plasmid on Ngn 1 mRNA expression.

RESULTSAn eukaryotic expression plasmid of Setd 7 was successfully constructed. Setd7 induced Ngn 1 mRNA expression and increased Ngn 1 promoter activity. Also, the knockdown of Setd 7 inhibited Ngn 1 mRNA expression.

CONCLUSIONHistone lysine methyltransferase Setd7 can enhance neuron differentiation marker gene Ngn 1 transcription.

Animals ; Basic Helix-Loop-Helix Transcription Factors ; genetics ; metabolism ; Gene Expression Regulation ; Genetic Vectors ; HEK293 Cells ; Histone-Lysine N-Methyltransferase ; genetics ; metabolism ; Humans ; Mice ; Nerve Tissue Proteins ; genetics ; metabolism ; Protein Methyltransferases ; genetics ; metabolism ; RNA, Messenger ; genetics ; Transfection

Calmegin is a testis-specific molecular chaperon playing a key role in spermatogenesis. However, the transcriptional regulatory mechanisms for calmegin expression are entirely unknown. Herein, we revealed that calmegin is transcriptionally regulated by histone deacetylase (HDAC) and CpG methyltransferase. The cDNA microarray analysis of the human fibrosarcoma cells treated with trichostatin A (TSA) showed an increased level of calmegin mRNA. The induction of calmegin mRNA by TSA was added by the treatment with 5-aza-2'-deoxycytidine (5'Aza- dC), implying that epigenetic alterations are involved in the transcriptional repression of the gene. Moreover, chromatin immunoprecipitation assay using an anti-acetyl-histone H3 antibody exhibited that the proximal region (-152~-31) of the calmegin promoter is responsible for HDAC-mediated transcriptional repression of the gene. These results demonstrate that calmegin expression is regulated by HDAC and CpG methyltransferase in a coordinative way.
Animals ; Calcium-Binding Proteins/*genetics ; Cell Line, Tumor ; *Gene Expression Regulation ; Histone Deacetylases/*metabolism ; Humans ; Male ; Methyltransferases/*metabolism ; Mice ; Molecular Chaperones/*genetics ; Organ Specificity ; Promoter Regions (Genetics)/genetics ; Research Support, Non-U.S. Gov't ; Testis/*metabolism ; *Transcription, Genetic

BACKGROUNDHistone deacetylase (HDAC) inhibitors are a group of small chemical molecules that inhibit histone deacetylase. At cell level, HDAC inhibitors have multiple biological effects such as cell cycle arrest, apoptosis, cell differentiation and auotophagy. At molecular level, HDAC inhibitors cause histone and nonhistone acetylation and induce gene expression. HDAC inhibitors are widely used in cancer therapy because of its function of inducing apoptosis. However, the mechanisms of apoptosis effect are not fully understood. TSA is a classical HDAC inhibitor and widely used in epigenetic and anti-cancer research. In this study, we selected Trichostatin A (TSA) to investigate the mechanisms of HDAC inhibitors apoptotic effect on cancer cells.

METHODSCervical cancer cell lines such as Hela, Caski and normal human keratinocyte line HaCaT were treated with various concentrations of TSA. Crystal violent assay and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed to determine cell number. PARP cleavage and FITC-AnexinV were performed to determine apoptosis. DNA-methyltransferase (DNMT)1, DNMT3A and DNMT3B were determined by regular PCR, qPCR and Western Blotting. Small interfering RNA (SiRNAi) was used to knock down DNMT3B.

RESULTSHDAC inhibitors only induce cervical cancer cell apoptosis. At 1 µmol/L of TSA, 86% of Hela cell and 76% of Caski went apoptosis. For normal cells, HDAC inhibitors have no cytotoxic effect at therapeutic dosage, (90.0 ± 8.4)% of normal cell survive after treated with 1 µmol/L of TSA. We compared 1 µmol/L group with untreated control with t-test. There was no significance between 1 µmol/L group and untreated control for normal cell (P > 0.05). HDAC inhibitors decreased DNMT3B in cancer cell but not in normal cell. Manually knock-down of DNMT3B induced Hela and Caski cell apoptosis. More than 99% of Hela and Caski cell went apoptosis after deprived of DNMT3B.

CONCLUSIONSDNMT3B was essential to cervical cancer cell survival. Down-regulated DNMT3B by HDAC inhibitors may play an important role in the toxicity of HDAC inhibitors on cervical cancer cells.

Apoptosis ; drug effects ; genetics ; Cell Line ; Cell Line, Tumor ; DNA (Cytosine-5-)-Methyltransferases ; genetics ; metabolism ; Female ; HeLa Cells ; Histone Deacetylase Inhibitors ; pharmacology ; Humans ; Hydroxamic Acids ; pharmacology ; Uterine Cervical Neoplasms ; enzymology ; genetics

We have investigated the function and mechanisms of the CARM1-SNF5 complex in T3-dependent transcriptional activation. Using specific small interfering RNAs (siRNA) to knock down coactivators in HeLa alpha2 cells, we found that coactivator associated arginine methyltransferase 1 (CARM1) and SWI/SNF complex component 5 (SNF5) are important for T3-dependent transcriptional activation. The CARM1- SWI/SNF chromatin remodeling complex serves as a mechanism for the rapid reversal of H3-K9 methylation. Importantly, siRNA treatment against CARM1 and/or SNF5 increased the recruitment of HMTase G9a to the type 1 deiodinase (D1) promoter even with T3. Knocking- down either CARM1 or SNF5 also inhibited the down- regulation of histone macroH2A, which is correlated with transcriptional activation. Finally, knocking down CARM1 and SNF5 by siRNA impaired the association of these coactivators to the D1 promoter, suggesting functional importance of CARM1- SNF5 complex in T3-dependent transcriptional activation.
Chromosomal Proteins, Non-Histone/*physiology ; DNA-Binding Proteins/*physiology ; Hela Cells ; Histone-Lysine N-Methyltransferase/*metabolism ; Histones/metabolism ; Humans ; Iodide Peroxidase/metabolism ; Methylation ; Promoter Regions, Genetic ; Protein Methyltransferases ; Protein-Arginine N-Methyltransferase/*physiology ; Receptors, Thyroid Hormone/*physiology ; Transcription Factors/*physiology ; *Transcriptional Activation

This study is to investigate the effect of phenylhexyl isothiocyanate (PHI), which has been proved to be a novel histone deacetylase inhibitor (HDACi) recently, on gene p15 de novo expression in acute leukemia cell line Molt-4, and to further study its potential mechanism. Modified methylation specific PCR (MSP) was used to screen p15-M and p15-U mRNA. DNA methyltransferasel (DNMT1), 3A (DNMT3A), 3B (DNMT3B) and p15 mRNA were measured by RT-PCR. P15 protein was detected by Western blotting. Hypermethylation of gene p15 was reversed and activation transcription of gene p15 in Molt-4 was de novo after 5 days exposure to PHI in a concentration dependent manner. DNMT1 and DNMT3B were inhibited by exposure to PHI for 5 days (P < 0.05). Alteration of DNMT3A was not significant. It is showed that PHI could reverse hypermethylation of gene p15 and transcriptional activation of gene p15 is de novo by PHI. It may result from down-regulating DNA methyltransferases, DNMT1 and DNMT3B, or up-regulating the histone acetylation that allows chromatin unfolding and the accessibility of regulators for transcriptional activation in the p15 promoter.
Cell Line, Tumor ; Cyclin-Dependent Kinase Inhibitor p15 ; genetics ; metabolism ; DNA (Cytosine-5-)-Methyltransferases ; genetics ; metabolism ; DNA Methylation ; Histone Deacetylase Inhibitors ; pharmacology ; Humans ; Isothiocyanates ; pharmacology ; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma ; genetics ; metabolism ; pathology ; RNA, Messenger ; metabolism ; Repressor Proteins ; genetics ; metabolism

OBJECTIVE: To analyze the mdr-1 gene promoter methylation and histone acetylation status in both MCF-7/Adr and MCF-7 cells and to preliminarily explore the epigenetic mechanism of multidrug resistance in breast cancer. METHODS: mdr-1 gene promoter methylation status of the 2 cell lines was detected by methylation-sensitive PCR. mRNA expression of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs) was detected by real-time quantitative PCR. Acetylation level of histone H3 and H4 was examined by optical density assay. RESULTS: Promoter hypermethylation of mdr-1 gene was observed in MCF-7 cells whereas hypomethylation was found in MCF-7/Adr cells. Expression of DNMT1, DNMT3a, and DNMT3b mRNA in MCF-7/Adr cells significantly decreased compared with that of MCF-7 cells (P<0.05). H3 and H4 histone acetylation levels of MCF-7/Adr cells were obviously higher than those of the MCF-7 cells (P<0.01). Expression of HDAC1, HDAC2, HDAC7, and Sirtuin type 1 (SIRT1) mRNA in MCF-7/Adr cells was significantly reduced (P<0.05). CONCLUSION Hypomethylation of the promoter region of mdr-1 gene, high H3 and H4 histone acetylation, and low mRNA expression of DNMTs and HDACs may be important epigenetic factors for the development of MDR in MCF-7/ Adr cells.
ATP Binding Cassette Transporter, Subfamily B, Member 1 ; genetics ; Acetylation ; Breast Neoplasms ; pathology ; Cell Line, Tumor ; DNA (Cytosine-5-)-Methyltransferase 1 ; DNA (Cytosine-5-)-Methyltransferases ; genetics ; metabolism ; DNA Methylation ; genetics ; Drug Resistance, Multiple ; genetics ; Drug Resistance, Neoplasm ; genetics ; Epigenesis, Genetic ; Female ; Histone Deacetylases ; genetics ; metabolism ; Histones ; chemistry ; Humans ; Promoter Regions, Genetic ; genetics ; RNA, Messenger ; genetics ; metabolism