Regulation of 3D genome organization, transcription and histone H3K9me2 by histone H3K9 methyltransferases [HiC]

Histone H3 lysine 9 dimethylation (H3K9me2) is a highly conserved silencing epigenetic mark. Chromatin marked with H3K9me2 forms large domains in mammalian cells and overlaps well with lamina-associated domains and the B compartment defined by Hi-C. However, the role of H3K9me2 in 3-dimensional (3D) genome organization remains unclear. We investigated genome-wide H3K9me2 distribution, transcriptome, and 3D genome organization in mouse embryonic stem cells following the inhibition or depletion of five H3K9 methyltransferases (MTases): G9a, GLP, SETDB1, SUV39H1, and SUV39H2. H3K9me2 was regulated by all five MTases; however, H3K9me2 and transcription in the A and B compartments were regulated by different MTases. H3K9me2 in A compartments was primarily regulated by G9a/GLP and SETDB1, while H3K9me2 in the B compartments was regulated by all five MTases. Furthermore, decreased H3K9me2 correlated with changes to the more active compartmental state that accompanied transcriptional activation. Examination of H3K9me2, H3K9me3, transcriptome and 3D genome organization in H3K9 methyltransferase deficient mESCs and iMEFs