Linker histones consolidate heterogenous nucleosome fiber contacts by linking together multiple nucleosomes

Abstract

Abstract The consensus mode for linker histone (H1) association coincides with ‘on-dyad’ binding to an individual nucleosome, making it challenging to rationalize the chromatin dynamics and compacting activities of H1 in the context of a highly heterogeneous structural scaffold. Here, we investigate the activity of the somatic H1 variants by conducting crystallographic analysis of nucleosomal assemblies and characterization of nucleosome array condensates, which recapitulate long-range nucleosome fiber interactions in chromatin. H1 is observed to associate variant-dependently with nucleosomes through a diversity of binding modes that include linking multiple nucleosomes/fibers together. Binding versatility is facilitated by the proclivity of the H1 globular domain to recognize DNA structural motifs, which are similar between an individual nucleosome and specific niches within clusters of nucleosomes. We propose that linker histones support a structurally and functionally complex repertoire for chromatin regulation by assuming a variety of context-and variant-dependent DNA binding modes.