Revealing the Role of Histone Tails in Controlling Nucleosome Assembly and Chromatin Compaction

Abstract

Histone proteins are essential to the construction of chromatin fiber and controlling its conformational state for the regulation of gene expression. DNA wrapping over histone octamer forms a nucleosome as the basic unit of chromatin fiber and understanding how the nucleosome wrapping/positioning and the compaction of nucleosome arrays are controlled is the key to understanding epigenetic gene regulation. Each histone protein subunit has unstructured tail region, which is known as multiplexed target of epigenetic modification. But we still lack knowledge about the role of the tail regions and the effect of each epigenetic modification on the chromatin structure and dynamics. We developed magnetic tweezers combined with single molecule fluorescence imaging to measure the mechanical properties and dynamics of nucleosomes and chromatin fibers. By using histone proteins with deleted tail regions or with epigenetic modification at specific residues, we try to figure out their role in controlling chromatin structure and dynamics. We present preliminary results from the measurement of the chromatin compaction and nucleosome unwrapping dynamics.