The structure of chromatin on the inactive X chromosome revealed by in situ electron cryogenic tomography

We observe an enrichment for histone H1-bound chromatosomes that are distributed to form the core of Xi chromatin domains. Moreover, we demonstrate that histone deacetylation demarcates chromatin domains. Specifically, perturbations that result in Xi histone hyperacetylation dissolve discrete chromatin-domain boundaries, resulting in a homogeneous chromatin distribution with a dense and ordered packing of nucleosomes.

Together, these findings illuminate the multiscale organisation of native facultative heterochromatin and the contributions of histone H1 and histone acetylation to this organisation. This study opens a new avenue for investigating how chromatin modification and structure relate to defined gene activity in near-native cells.