We are working to understand the influence of linker histone proteins on nucleosome and chromatin dynamics. Linker histone H1 is a highly abundant chromatin architectural protein with about 1 linker histone per nucleosome in human somatic cells. H1 binds to both DNA between nucleosomes (linker DNA) and near the dyad symmetry axis of the nucleosomes. H1 binding increases DNA wrapping within the nucleosome and compacts chromatin. There has been a significant focus on the structural changes H1 induces within nucleosomes and chromatin. However, much less is known about the influence of H1 on nucleosome and chromatin dynamics. We are investigating the influence of H1 on DNA unwrapping and TF binding within the nucleosome.
We find that nucleosomes remain highly dynamic in the presence of H1 and that H1 dissociation is not required for partial unwrapping of the DNA. We also find that the histone PTM, acetylation of H3 lysine 56, which increases DNA unwrapping, inhibits the influence of H1 on nucleosome unwrapping. This indicates that a histone PTM can define whether a specific nucleosome can be regulated by H1.