Artificial Modification of Histones and the Effect on Epigenetics

Abstract

In order for cells to package all of their genetic material, DNA is wrapped around eight histone proteins (two copies each of H2A, H2B, H3, and H4) to make up the nucleosome. Nucleosomes are the fundamental building blocks of chromatin, which is the first step of compaction and the first level of gene regulation. The phrase “histone code” was coined in regard to those molecular processes that regulate the eukaryotic genome. Further study of the “histone code” and epigenetics has revolutionized the scientific community's understanding of the regulation of gene expression. The Histone H4 N-terminal tail has a region called the basic patch. It is thought that this region is a hub for histone-modifying activity. Histone H2B lysine-123 (H2BK123) is monoubiquitinated and this modification is required for the proper regulation of transcription. In this study, H2BK123ub levels were measured and preparations were made to develop a novel amber codon suppression screen to study the histone H4 basic patch. The overarching goal of the study was to artificially modify histones and their post-translational modification processes in order to understand their mechanisms and therefore better understand epigenetics.