H3K9me12

H3K9me12 is not a recognized histone modification in standard epigenetics nomenclature. Lysine 9 of histone H3 can be mono-, di-, or tri-methylated, referred to as H3K9me1, H3K9me2, and H3K9me3. A designation of H3K9me12 would imply twelve methyl groups on a single residue, which is chemically implausible and has no basis in established histone mark catalogs.

Histone H3 lysine 9 methylation is a key repressive signal that contributes to heterochromatin formation and transcriptional silencing. H3K9me3 is enriched in constitutive heterochromatin, especially pericentromeric regions, and is recognized by HP1 proteins. H3K9me2 marks broader repressive domains and can occur in euchromatic contexts. Methyltransferases such as SUV39H1/2 and SETDB1 deposit H3K9me3, while G9a and GLP predominantly generate H3K9me2. Demethylases including KDM3A/B (JMJD1) and KDM4 family (JMJD2) can remove these marks, enabling gene activation.

Readers, co-factors, and DNA methylation interplay regulate silencing. HP1 proteins bind H3K9me3 and recruit additional silencing machinery; crosstalk with DNA methyltransferases helps maintain repressive chromatin. These marks are dynamic during development and differentiation and can be disrupted in disease, including cancer and aging.

If you encountered H3K9me12 in a reference, it likely reflects a typographical error or a misinterpretation of H3K9me3/me2. For reliable information, consult standard resources on H3K9me2 and H3K9me3.