Nucleosome Interaction Surface of Linker Histone H1c Is Distinct from That of H10

Eric M George,Tina Izard,David T Brown,Stephen D Anderson

doi:10.1074/jbc.m110.108639

Abstract

The fully organized structure of the eukaryotic nucleosome remains unsolved, in part due to limited information regarding the binding site of the H1 or linker histone. The central globular domain of H1 is believed to interact with the nucleosome core at or near the dyad and to bind at least two strands of DNA. We utilized site-directed mutagenesis and in vivo photobleaching to identify residues that contribute to the binding of the globular domain of the somatic H1 subtype H1c to the nucleosome. As was previously observed for the H1(0) subtype, the binding residues for H1c are clustered on the surface of one face of the domain. Despite considerable structural conservation between the globular domains of these two subtypes, the locations of the binding sites identified for H1c are distinct from those of H1(0). We suggest that the globular domains of these two linker histone subtypes will bind to the nucleosome with distinct orientations that may contribute to higher order chromatin structure heterogeneity or to differences in dynamic interactions with other DNA or chromatin-binding proteins.

Highlights

The nucleosome is the fundamental repeating unit of eukaryotic chromatin [1, 2]
We suggest that the globular domains of these two linker histone subtypes will bind to the nucleosome with distinct orientations that may contribute to higher order chromatin structure heterogeneity or to differences in dynamic interactions with other DNA or chromatin-binding proteins
X-ray crystallographic data of H1-containing nucleosomes has not been reported to date, and there is little direct structural information regarding the exact location of the linker histone on the nucleosome [16, 17, 27,28,29]

Summary

Introduction

The nucleosome is the fundamental repeating unit of eukaryotic chromatin [1, 2]. Two molecules each of the four core histones, H2A, H2B, H3, and H4, form an octamer around which is wrapped 147 bp of DNA to form the nucleosome core particle [3, 4]. We utilized site-directed mutagenesis and in vivo photobleaching to identify residues that contribute to the binding of the globular domain of the somatic H1 subtype H1c to the nucleosome. Despite considerable structural conservation between the globular domains of these two subtypes, the locations of the binding sites identified for H1c are distinct from those of H10.

Results

Conclusion