Uncovering the Functional Effects of Cancer Associated Mutations on Histone H2B
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Authors
Macklem, Austin
Date
2024-10-18
Type
thesis
Language
eng
Keyword
Cancer , Genetics , Epigenetics , Chromatin , Histones
Alternative Title
Abstract
In eukaryotes, DNA is wrapped into chromatin, a nucleoprotein structure that controls DNA-templated processes like DNA replication, transcription, and DNA repair. Nucleosomes are the basic unit of chromatin and consist of 146 base pairs of DNA wrapped around two copies of histone H2A, H2B, H3, H4. The increased availability of cancer genomics datasets has revealed a large repertoire of mutations on histone genes and shown that these occur frequently in cancer patients. Although, the significance of the large histone gene mutational landscape remains understudied, some of these mutations (H3-K27M, H3-K36M and H3-G34R) have been shown to drive oncogenesis and are now used as biomarkers of specific tumor types. My project aims to advance our understanding of the functional consequences of cancer-associated histone H2B mutations using Saccharomyces cerevisiae as a model system. Focusing on mutations that fall on residues conserved between yeast and humans, I made several important discoveries. Using computational tools such as SAAMBE and SAMPDI, I found that histone H2B missense mutations are predicted to have similar destabilizing effects in human and yeast nucleosomes and identified htb1-Y86C/D as mutations that are predicted to disrupt histone-histone interactions. Focusing on a panel of histone H2B missense mutations, I generated a library of yeast strains carrying only mutant or mutant and wildtype versions of HTB1 (one of two genes that codes for histone H2B is yeast). Using this library, I identified several histone H2B missense mutations that disrupt normal cellular function. Examining these effects further, I found that the htb1-G107R mutant disrupted H3-K79me3 levels, increased the background mutation rate, and produced growth defects similar to the htb1-E79K mutant. The latter is particularly interesting given that the htb1-E79K mutation mirrors the most frequent histone H2B mutation observed in cancer patients, findings that suggests that different histone mutations may disrupt function through shared mechanisms. Consistent with the later, molecular dynamic simulations of H2B-G107R and H2B-E79K mutant nucleosomes showed similar alterations to H2B-H4 contacts. Overall, this work uncovered a wide range of molecular defects produced by histone H2B missense mutations, laying the foundation to ultimately reveal how histone mutations contribute to cancer biology.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.