Tumorigenic, oncogenic, and cell cycle effects of H2A/H3 oncohistone mutations explored through structural modeling and analysis in Saccharomyces cerevisiae Restricted; Files Only

Mwonga, Diane (Spring 2021)

Permanent URL: https://etd.library.emory.edu/concern/etds/h989r4498?locale=en
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Abstract

Oncohistone mutations are primarily missense mutations that occur in the core histones genes that encode the building blocks of the nucleosome complex. The histone proteins that comprise nucleosomes are highly conserved through evolution and are critical for nearly all DNA transactions. An increased understanding of how these oncohistone mutations affect cellular properties such as growth, regulation, chromatin structure, and post-translational modifications (PTMs) of histones is critical to developing novel drug therapeutic agents to treat cancers. Further research in mutations in the histone H2A and H3 genes can facilitate the development of novel therapeutics for head, neck, and hematological cancers. In the present study, I employ two complementary approaches; 1) I analyze known oncohistones (H3) using a budding yeast model, and 2) explore potential novel oncohistones (H2A) modeled using PyMOL software to generate hypotheses about the consequences of these previously unstudied missense mutations. Through this study, we examine the consequences of histone H3 and H2A gene mutations, providing insight into oncohistone mutations in tumor and cancer pathways in these core histone proteins. H3 oncohistones were studied in vivo in a Saccharomyces cerevisiae model. H2A oncohistones were studied through remote and computational analyses of protein structure through nucleosome modeling. Taken together, these oncohistone studies could help to expand our understanding of how oncohistone mutations impact cell growth and support oncogenic transformation.

Table of Contents

Chapter 1: Introduction................................................................................................................. 1

The Nucleosome Complex and Histones................................................................................. 1

Oncohistones.............................................................................................................................. 2

Histone Post-translational Modifications (PTMs) ................................................................. 4

An S. cerevisiae model to study functional consequences of oncohistones.......................... 4

Novel Oncohistones................................................................................................................... 5

Chapter 2: Materials and Methods................................................................................................ 8

Development of S. cerevisiae models to study oncohistones ................................................. 8

S. cerevisiae growth assays....................................................................................................... 8

Novel oncohistone computational modeling ........................................................................... 9

Chapter 3: Results........................................................................................................................ 11

A Budding Yeast Model to Characterize Know Oncohistone Proteins............................. 11

H3 oncohistone variants H3K36R, H3K36M, H3G34W, H3G34L, H3G34R, and H3G34V show growth defects on media containing YP glycerol, hydroxyurea, phleomycin, caffeine, and formamide ................................................................................... 11

Novel Onocohistones............................................................................................................... 15

Human Histone H2A shares 73% identity with S. cerevisiae Histone H2A...................... 15

Histone H2A residue E57i’s accessible at the surface of the Octamer Protein Complex. 16

H2AE57K & H2AE57Q Mutant exhibit various steric clashes, van der Waals, hydrophobic, polar, and hydrogen bonding forces with surrounding residues................ 17

Chapter 4: Discussion.................................................................................................................. 19

REFERENCES............................................................................................................................ 25

Figures.......................................................................................................................................... 28

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