Methionine Adenosyltransferase II-dependent Histone H3K9 Methylation at the COX-2 Gene Locus

Methionine adenosyltransferase (MAT) synthesizes S-adenosylmethionine (AdoMet), which is utilized as a methyl donor in transmethylation reactions involving histones. MATIIα, a MAT isozyme, serves as a transcriptional corepressor in the oxidative stress response and forms the AdoMet-integrating transcription regulation module, affecting histone methyltransferase activities. However, the identities of genes regulated by MATIIα or its associated methyltransferases are unclear. We show that MATIIα represses the expression of cyclooxygenase 2 (COX-2), encoded by Ptgs2, by specifically interacting with histone H3K9 methyltransferase SETDB1, thereby promoting the trimethylation of H3K9 at the COX-2 locus. We discuss both gene-specific and epigenome-wide functions of MATIIα. Background: MATII biosynthesizes AdoMet, which supplies methyl group for methylation of molecules, including histone. Results: MATII interacts with histone methyltransferase SETDB1 and inhibits COX-2 gene expression. Conclusion: AdoMet synthesis and histone methylation are coupled on chromatin by a physical interaction of MATII and SETDB1 at the MafK target genes. Significance: MATII may be important for both gene-specific and epigenome-wide regulation of histone methylation.