Development of Tools to Assess The Link between Histone Modification States And Chromatin Dynamics

Abstract

The installation, removal, and recognition of histone post-translational modifications (PTMs) are largely responsible for dynamic changes that characterize the chromatin landscape. The phosphorylation of tyrosine-41 on histone H3, a lessercharacterized modification in nonvariant mammalian histones, is known to be correlated with increased transcription of a key hematopoietic gene. Despite indications that H3Y41ph plays a regulatory role in transcription, a picture of mechanistic details regarding the way in which it alters chromatin structure has yet to emerge. In this study, I present the development of a set of chemical biology tools to probe the dynamics of histone-DNA interactions. Specifically, native chemical ligation (NCL), along with solid phase peptide synthesis (SPPS) and recombinant protein production, is employed to reconstitute nucleosomes incorporating wild type and designer histones. Results from restriction enzyme accessibility assays (REAA) suggest that the placement of a phosphate group at tyrosine-41 of H3, introducing a significant negative charge at this site, may be responsible for increased transient detachment of DNA from the nucleosome, giving rise to greater accessibility by transcription factors. The development of this methodology continues to promise broader possibilities for epigenetics and disease studies.