question: Which post-translational histone modifications are characteristic of constitutive heterochromatin?
answer: H3K9me3 is the major marker of constitutive heterochromatin. Other histone methylation marks usually found in constitutive heterochromatin, are H4K20me3 and H3K79me3. Classical histone modifications associated with heterochromatin include H3K9me2, H3K27me1 and H3K27me2. Histone H3 trimethylation at lysine 36 is associated with constitutive and facultative heterochromatin. H3S10 phosphorylation marks constitutive heterochromatin during interphase in early mouse embryos until the 4-cell stage