H1 is the linker histone and is important for chromatin condensation, it binds to the nucleosomal core particles and protects the free linker DNA (∼20 bp) between each nucleosome. H1 can potential to fine-tune transcription in a locus-specific manner. H1 is involved in several processes, its interaction partners include: pre-mRNA splicing factors; histone chaperones; components of the transcription machinery and DNA-damage response factors.
There a 12 subtypes of the H1 linker histone, and they are thought to have specific functions, making H1 the most divergent histone protein family. Like other histones, H1s are extensively post-translationally modified with modifications including: methylation, acetylation, ubiquitination, formylation, poly-ADP ribosylation and phosphorylation.
Changes in H1 composition and expression levels are seen in several cancers and other diseases.