Project description:Chronic hypoxia inhibits apoptosis to enhance survival of cancer cells. The mechanisms that prevent apoptosis under hypoxia are unclear. Here, we show that hypoxia induced G9a, a lysine methyltransferase, which methylates a tumor suppressor, Runt-related transcription factor 3 (RUNX3) at lysines 129 and 171. G9a-mediated methylation reduced transcriptional activity of RUNX3 by inhibiting interactions with its transcriptional cofactors, the core-binding factor-beta (CBF-beta) and p300, and also decreased the protein level of RUNX3 via Smurf1-mediated proteasomal degradation. Through ChIP-seq and gene expression profiling, G9a-mediated methylation inhibited expression of genes involved in apoptosis, thereby enhancing survival and proliferation of cancer cells both in vitro and vivo. Our results suggest G9a-dependent methylation of RUNX3 as a therapeutic target to control tumor growth.
Project description:Chronic hypoxia inhibits apoptosis and cell cycle arrest in cancer cells, leading to cell survival, proliferation and angiogenesis. The mechanism for anti-apoptosis and cell proliferation in hypoxic cancer cells is still elusive. Here, we showed that hypoxia inactivates Runt-related transcription factor 3 (RUNX3), which is known to play as a tumor suppressor to induce apoptosis and cell cycle arrest in various cancers. RUNX3 is methylated under hypoxic conditions at lysines (K) 129 and 171 through its interaction with methyltranferase G9a. Gene expression profiling revealed that the mutations of K129 and 171 in RUNX3 induced the expression of genes related to apoptosis and cell cycle arrest under hypoxic conditions, indicating critical roles of the RNUX methylation in anti-apoptosis and cell proliferation. Moreover, K129 and 171 mutants, compared to G9a or G9a+RUNX3 control, showed significant reduction in apoptotic ability and tumor progression in xenograft models. Therefore, G9a-dependent methylation of RUNX3 is a novel target to inhibit cell proliferation and anti-apoptosis under hypoxic conditions during tumorigenesis.
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis. Examination of gene expression changes in G9a KO brown preadipocytes
Project description:PPAR? promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPAR? locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPAR?. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPAR? promoter, which promotes PPAR? expression. Interestingly, G9a represses PPAR? expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPAR? expression and facilitating Wnt10a expression, G9a represses adipogenesis. Examination of 3 different histone modification changes in 3T3-L1 preadipocytes
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis.
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis.
Project description:Gene expression in eukaryotes is tightly linked to the methylation state of specific lysine residues within the N-terminal region of the core histone proteins. While the mechanisms connecting histone lysine methylation to effector protein recruitment and control of gene activity are increasingly well understood, it remains unknown whether non-histone chromatin proteins are targets for similar modification-recognition systems. Here we show that histone H3 and the H3 methyltransferase G9a share a conserved methylation motif that is both necessary and sufficient to mediate in vivo interaction with the potent epigenetic regulator Heterochromatin Protein 1 (HP1). As with H3, G9a-HP1 interaction is dependent on lysine methylation and can be reversed by adjacent phosphorylation. NMR analysis demonstrates that the HP1 chromodomain recognizes methyl-G9a through a binding mode similar to that used in recognition of methyl-H3, and that adjacent phosphorylation directly antagonizes G9a-HP1 interaction. In addition to uncovering the chromodomain as a generalized methyl-lysine binding module, these data identify histone-like modification cassettes (or âhistone mimicsâ) as an entirely new class of non-histone methylation targets, and directly demonstrate the relevance of the principles underlying the histone code to the regulation of non-histone proteins. Experiment Overall Design: Two independent Affymetrix gene expression microarray analyses were performed on samples from G9a-deleted MEFs reconstituted with empty vector (delta), wild type FLAG-G9a (WT), FLAG-G9a K165A (K165A) or FLAG-G9a H1093K catalytic mutant (H1093K).
Project description:G9a and GLP lysine methyltransferases form a heterodimeric complex that is responsible for the bulk of cellular mono- and di-methylation on histone H3 lysine 9 (H3K9me1/me2). Widely Interspaced Zinc finger (WIZ) associates with the G9a/GLP protein complex, but its role in lysine methylation is poorly defined. Here, we show that WIZ regulates global H3K9me2 levels through a mechanism that involves retention of G9a on chromatin. We also show that WIZ-mediated chromatin loss of G9a/GLP results in altered gene expression and protein-protein interactions that are distinguishable from that of using a molecule-induced enzymatic inhibitor towards G9a/GLP – thus providing evidence that the G9a/GLP/WIZ complex has unique functions when bound to chromatin that are independent of the H3K9me2 mark DMSO, UNC0638, NS, and siWIZ treatments to HEK293T cells, assessing G9a and H3K9me2 localization, each performed in duplicate, plus one input control for each cell condition. 30 samples total.