The Effects of Site Specific Histone Modifications on Nucleosomal DNA Accessibility

Abstract

Chromatin accessibility is the ability of nucleosomal DNA to be physically accessed by cellular biomachinery. Accessibility of chromatin is controlled by a slew of post translational modifications to histone proteins, DNA, and chromatin-binding factors. This growing field of research has become increasingly important as chromatin accessibility has a large effect on transcription and gene regulation. Gene and cell cycle regulation must be understood to properly study their misregulation which commonly occurs in most, if not all, cancers. Thus, understanding the organization and regulation of the chromatin state by post translational modifications plays an important role in understanding the dysfunction of cancerous cells. The most basic unit of chromatin is the nucleosome core particle. The nucleosome core particle is made up of an octamer that has two copies each of the 4 histone proteins H2A, H2B, H3, and H4 with DNA wrapping around the octamer itself. It is on the N-terminal tails of these histone proteins that many post-translational modifications take place the regulate the chromatin state. In this study, the effect of histone lysine acetylation on the DNA-histone core interaction will be assessed by its thermal stability and accessibility of nucleosomal DNA to Pst1 Digestion. We propose to assay singly acetylated mononucleosomes at the following sites: H2A: K5; H2B: K5, K12, K15, and K20; H3: K9, K14, K18, K23, K27, K36, K37, K64, K56, K79, K115, and K122; H4: K5, K8, K12, and K16. We predict that, as previously shown with nu′-H3K18ac and nu′-H3K36ac acetylation at lysine sites will facilitate unwrapping of nucleosomal DNA.