Fundamental Role Of The H2A.Z C-Terminal Tail In The Formation Of Constitutive Heterochromatin

Abstract

H2A.Z-nucleosomes are present in both euchromatin and heterochromatin and it has proven difficult to interpret their disparate roles in the context of their stability features. Using an in situ assay of nucleosome stability and DT40 cells expressing engineered forms of the histone variant we show that native H2A.Z, but not C-terminally truncated H2A.Z (H2A.Z{Delta}C), is released from nucleosomes of peripheral heterochromatin at unusually high salt concentrations. H2A.Z and H3K9me3 landscapes are reorganized in H2A.Z{Delta}C-nuclei and overall sensitivity of chromatin to nucleases is increased. These tail-dependent differences are recapitulated upon treatment of HeLa nuclei with the H2A.Z-tail-peptide (C9), with MNase sensitivity being increased at specific regions including promoters. Introduced into live cells C9 elicits down-regulation of [~]560 genes with nonrandom chromosomal band-localization and pathway-spectrum. Thus, tail-dependent heterogeneity of H2A.Z-nucleosomes is revealed at all organization levels of chromatin and epigenetic modulation can be achieved by targeting molecular interactions involving its C-terminal tail.