G9A (EHMT2)

Class

Epigenetic modulator (histone methyltransferase inhibitor)

G9A, also known as EHMT2, is an enzyme called a histone methyltransferase. It chemically tags a specific site on histone proteins (the spools around which DNA is wound) by adding methyl groups to lysine 9 of histone H3. This modification, mainly in its mono- and di-methylated forms, is a hallmark of transcriptionally silent chromatin, meaning it helps keep certain genes switched off. G9A activity is important for normal development, cellular identity, and maintenance of quiescent (non-dividing) cell states. In disease, G9A-mediated silencing has been implicated in cancers, where it can shut down tumor-suppressor genes or genes required for cell differentiation, and in blood disorders where it contributes to keeping fetal hemoglobin genes turned off after birth. Small-molecule inhibitors of G9A aim to block its catalytic activity, reversing this repressive marking and allowing previously silenced genes to be re-expressed. This class of epigenetic modulator is of interest wherever reactivating a silenced gene program, rather than blocking an overactive signal, is the therapeutic goal, distinguishing it from more conventional receptor- or kinase-targeted approaches.