Few factors were associated with repressive modifications.
In a preliminary study, we found that AML1-MTG16, whexogenouslysly expressed in 32D cells, can induce aberrant myeloid phenotypes in association with repressive modifications at the chromatin of the Colony stimulating factor 1 receptor (Csf1r), an AML1-target gene encoding the macrophage colony stimulating factor receptor [ 19].
In line with the identification of putatively active cis-regulatory enhancer elements, Rxrα binding sites consistently colocalized with active H3K4me1 marks (84.1% in liver, 51.4% in brain, and 87.2% in small intestine), in contrast with H3K27me3 repressive modifications (1.7% in liver, 1% in brain, and 1% in small intestine).
Interestingly, in ESCs, PcG target loci exhibit a unique bivalent chromatin state in which H3 acetylation and H3K4 methylation, modifications normally associated with gene activity, co-exist with PcG-mediated repressive modifications.
As genomic repeats are known to be enriched for H3K9me3 and H4K20me3, chromatin modifications that are associated with heterochromatin, all ATRX-binding sites across the genome also were tested for association with these two repressive modifications.
When overexpressed, CBFβ induced an inhibition of activating histone modification marks concomitant with an increase in repressive modifications at MyoD target promoters.
The instructional role of H3K4me may be analogous to the role of H3K36 methylation's antagonism to H3K27me, as H3K4me has been noted to have a similarly antagonistic relationship with the repressive modification H3K9 methylation (for example, [ 71, 72]).
Another possibility is that mutational depletion of HP1 interferes with the repressive modification of chromatin in and around P elements in the genomes of test-cross offspring, with the result that these elements are mobilized by the P transposase, ultimately causing dysgenesis.
Specific repressive modifications associated with XCI in human and mouse were also observed in elephant (a distantly related placental mammal), as was accumulation of XIST RNA.
ESC are characterized by an unusual chromatin features where marks of open chromatin, such as acetylated H3K9 and trimethylated H3K4, are combined with repressive histone modifications like H3K27 trimethylation at some non-expressed genes [3], [4], [5], [6], [7].
Binding of ZNF703 to the TGFβ receptor II promoter was demonstrated by chromatin immunoprecipitation, and was associated with repressive chromatin modifications.
