Disease relevance of Ehmt2

• Role of histone methyltransferase G9a in CpG methylation of the Prader-Willi syndrome imprinting center [1].
• Lysine-specific murine histone H3 methyltransferase, G9a, was expressed and purified in a baculovirus expression system [2].
• In addition to the activation of G9a, our results also indicated that hypoxia increased H3K9me2 by inhibiting H3K9 demethylation processes [3].

High impact information on Ehmt2

• Histone methyltransferases G9a and GLP form heteromeric complexes and are both crucial for methylation of euchromatin at H3-K9 [4].
• GLP-deficiency led to embryonic lethality, a severe reduction of H3-K9 mono- and dimethylation, the induction of Mage-a gene expression, and HP1 relocalization in embryonic stem cells, all of which were phenotypes of G9a-deficiency [4].
• G9a is the major mammalian H3-K9 methyltransferase that targets euchromatic regions and is essential for murine embryogenesis [4].
• G9a-deficient ES cells also exhibited reduced H3-K9 methylation compared to wild-type cells, indicating that G9a is a dominant H3-K9 HMTase in vivo [5].
• Our results indicate that euchromatic H3-K9 methylation regulated by G9a is essential for early embryogenesis and is involved in the transcriptional repression of developmental genes [5].

Biological context of Ehmt2

• We found that H3-K9 methylation was drastically decreased in G9a-deficient embryos, which displayed severe growth retardation and early lethality [5].
• Substrate specificity and kinetic mechanism of mammalian G9a histone H3 methyltransferase [2].
• Ser-10 or Thr-11 phosphorylation resulted in poor methylation by G9a [6].
• G9a methylated synthetic peptide substrates containing the first 13 amino acids of histone H3 efficiently, although methylation, acetylation, or mutation of proximal Lys-4 amino acids reduced Lys-9 methylation [6].
• These results demonstrate that G9a is not essential for X-inactivation [7].

Anatomical context of Ehmt2

• However, analysis of this region in G9a mutant embryonic stem cells shows that these two methyl marks are dependent on different histone methyltransferases [8].
• Co-expression of G9a and H3 resulted in di- and tri-methylation of H3-K9, while siRNA-mediated knockdown of G9a in HeLa cells resulted in reduction of global H3-K9 di- and tri-methylation [9].

Associations of Ehmt2 with chemical compounds

• G9a histone methyltransferase plays a dominant role in euchromatic histone H3 lysine 9 methylation and is essential for early embryogenesis [5].
• GST fusion proteins containing various lengths of the histone H3 amino-terminal tail were used as substrates in the presence of recombinant G9a enzyme and AdoMet cosubstrate [6].
• A recombinant deletion mutant enzyme fused with maltose-binding protein (MBP-G9aDelta634) was used for steady-state kinetic analysis with various substrates and was compared with full-length G9a (G9aFL) [9].
• Hypoxic mimetics, such as deferoxamine and dimethyloxalylglycine, were also found to increase H3K9me2 as well as G9a protein and activity [3].
• To test whether HMT activity influences euchromatic cytosine methylation, we analyzed the DNA methylation status of approximately 2000 CpG-rich loci, which are predicted in silico, in G9a(-/-) embryonic stem cells by restriction landmark genomic scanning (RLGS) [10].
• As with methylation of H3 lysine 9, autocatalytic G9a methylation is necessary and sufficient to mediate in vivo interaction with the epigenetic regulator heterochromatin protein 1 (HP1), and this methyl-dependent interaction can be reversed by adjacent G9a phosphorylation [11].

Other interactions of Ehmt2

• G9a-mediated irreversible epigenetic inactivation of Oct-3/4 during early embryogenesis [12].
• We show by RNA fluorescence in situ hybridization (FISH) that expression of Snrpn, an imprinted gene regulated by the PWS-IC, is biallelic in G9a -/- ES cells, indicating loss of imprinting [1].
• Expression of Xist, which is crucial for the initiation of X-inactivation, was properly regulated and the inactivated X chromosome was stably maintained even in the absence of G9a [7].
• Zinc finger protein Wiz links G9a/GLP histone methyltransferases to the co-repressor molecule CtBP [13].
• Trimethylated peptides acted as a competitive inhibitor to substrate peptide and mixed inhibitor to AdoMet suggesting a random mechanism in a Bi Bi reaction for recombinant G9a where either substrate can bind first to the enzyme, and either product can release first [2].

Analytical, diagnostic and therapeutic context of Ehmt2

• Chromatin immunoprecipitation (ChIP) confirmed these loci to be targets of G9a, with decreased H3-K9 and/or -K27 dimethylation in the G9a(-/-) cells [10].

References