Role of histone modifications in the recruitment of remodeling complex RSC and lysine deacetylase Hst2 to chromatin

Abstract

Long DNA molecule must not just be somehow stored within a tiny cell but also be accessible by protein machineries to allow for timely execution of key cellular events such as chromatin compaction, cell division, transcription, etc. My PhD aimed at identifying the Histone protein modifications that recruit proteins to DNA using genetically encoded unnatural amino acid mutagenesis. For example, using pBPA as a crosslinker in budding yeast, I identified a novel preference of the RSC Chromatin Remodeler to H2B SUMOylated nucleosomes. This paves way for a better understanding into the intricate recruitment mechanisms of RSC to its substrate. In another project, I investigated the molecular mechanism behind the histone modification H3 S10 phosphorylation mediated chromosome compaction in mitosis. I showed that the interaction of Lysine Deacetylase, Hst2 with H3 S10ph is dependent on the 14-3-3 protein Bmh1. This phosphorylated Hst2-Bmh1 interaction is attuned with the cell cycle reaching its maximum in M phase. I could recapitulate the binding event in vitro by purifying genetically encoded phosphorylated Hst2. Furthermore, I also demonstrated that phosphorylation at C-terminal residues of Hst2 enhances its deacetylase activity releasing a previously identified autoinhibition of the enzyme. Hence, the data presented here address key mechanisms of chromosome compaction in mitosis.