Characterizing HP1-Driven Chromatin Compaction using Nuclear Magnetic Resonance Spectroscopy

Abstract

Eukaryotes package their DNA by wrapping it around a histone protein core to form a structure known as the nucleosome. The nucleosomes form large polymers called chromatin which separate into two distinct compartments in the nucleus. In constitutive heterochromatin compartments, chromatin displays dense compaction and dampened gene expression. Heterochromatin protein 1 (HP1) is a multivalent chromatin binding protein enriched at these heterochromatin sites. It is known that HP1 is capable of compacting single chromatin strands and cross-linking separate strands. Here we map the structural and biophysical properties of HP1 in vitro as it interacts with differentially modified semi-synthetic chromatin. Nuclear magnetic resonance spectroscopy provides the selectivity to study HP1 in dense chromatin networks while resolving residue-specific biophysical changes. These results provide insight into the function of HP1 in near-physiological chromatin environments.