Date of Award
Doctor of Philosophy (PhD)
It is well established that chromatin is a destination and source for signal transduction affecting all types of DNA metabolism. Histone proteins in particular are extensively post-translationally modified (PTM), and many of these individual modifications have been studied in depth. I have been interested in how the complex repertoire of histone PTMs are co-regulated to generate combinations with meaningful physiological outcomes. One important mechanism is “crosstalk” between pre-existing histone PTMs and enzymes that add or remove subsequent modifications on chromatin. It has been previously shown that H3 lysine 4 methyltransferases involved in transcriptional activation are stimulated and repressed by H2Bub and H2Aub, respectively. Here, using chemically-defined “designer” mononucleosomes, I tested whether nucleosomal H2BK120ub and H2AK119ub influence the activity of a well-studied histone methyltransferases complex that is repressive to transcription, Polycomb Repressive Complex 2 (PRC2). I also built upon previous studies of direct enzymatic crosstalk between histone ubiquitylation and H3 lysine 79 methyltransferase, Dot1L, by investigating the plasticity of ubiquitin position in stimulation of Dot1L methyltransferase activity. Finally, using designer mononucleosomes containing H3 phosphoserine mimetics, crosstalk studies with PRC2 methyltransferase uncovered a putative novel methyl/phos switch specific to the histone variant H3.3 These studies address the specificity of crosstalk between pre-existing post-translational modifications and subsequent methylation, and thereby strengthen our understanding of mechanisms to establish and maintain functional combinations of histone modifications in chromatin.
Whitcomb, Sarah J., "Using "Designer" Nucleosomes to Study Enzymatic Crosstalk Between Histone Ubiquitylation and Histone Methyltransferases" (2012). Student Theses and Dissertations. 244.