Histone H3K9Me2 (3-17) is a peptide fragment of histone H3 that corresponds to amino acid residues 4-18 of the human histone H3 sequence. Dimethylation of histone H3 at lysine 9 is associated with transcriptional repression.1 Heterochromatin protein 1-α (HP1-α), HP1-β, and HP1-γ selectively bind histone H3 N-terminal peptides containing dimethylated lysine 9 over unmodified lysine 9.2 In mouse embryos, maternal chromatin containing H3K9Me2 is bound by PGC7, which preserves DNA methylation and protects 5-methylcytosine from conversion to 5-hydroxymethylcytosine.3
References
1. Lienert, F., Mohn, F., Tiwari, V.K., et al. Genomic prevalence of heterochromatic H3K9me2 and transcription do not discriminate pluripotent from terminally differentiated cells. PLoS Genet. 7(6), e1002090 (2011).
2. Lachner, M., O'Carroll, D., Rea, S., et al. Methylation of histone H3 lysine 9 creates a binding site for HP1 proteins. Nature 410(6824), 116-120 (2001).
3. Nakamura, T., Liu, Y.-J., Nakashima, H., et al. PGC7 binds histone H3K9me2 to protect against conversion of 5mC to 5hmC in early embryos. Nature 486(7403), 415-419 (2012).