Author ORCID Identifier
https://orcid.org/0000-0002-3096-7867
Date of Graduation
5-2018
Document Type
Dissertation (PhD)
Program Affiliation
Epigenetics and Molecular Carcinogenesis
Degree Name
Doctor of Philosophy (PhD)
Advisor/Committee Chair
Taiping Chen, Ph.D.
Committee Member
Mark T. Bedford, Ph.D.
Committee Member
Sharon Y. R. Dent, Ph.D.
Committee Member
Kevin M. McBride, Ph.D.
Committee Member
Gregory K. Wilkerson, D.V.M., Ph.D., D.A.C.V.P.
Abstract
DNA methylation is an essential epigenetic modification in mammals, as it plays important regulatory roles in multiple biological processes, such as gene transcription, maintenance of chromosomal structure and genomic stability, genomic imprinting, retrotransposon silencing, and X-chromosome inactivation. Dysregulation of DNA methylation is associated with various human diseases. For example, cancer cells usually show global hypomethylation and regional hypermenthylation, which have been implicated in genomic instability and tumor suppressor silencing, respectively. Although great progress has been made in elucidating the biological functions of DNA methylation over the last several decades, how DNA methylation patterns and levels are regulated and dysregulated is not well understood. This dissertation focuses on the molecular mechanisms involved in the regulation of DNA methylation during mammalian development and in cancer. Using mouse embryonic stem cells (mESCs), an ideal model system for studying DNA methylation, I have discovered novel regulatory mechanisms that play important roles in de novo and maintenance DNA methylation. In one project, I show that Dnmt3L, a key regulator of de novo methylation, facilitates Dnmt3a-mediated methylation by stabilizing Dnmt3a2, the major Dnmt3a isoform in mESCs, thus uncovering a new role for Dnmt3L and providing a plausible explanation for the functional specificity of Dnmt3L. In a separate project, I demonstrate that PRMT6, an arginine methyltransferase responsible for asymmetric dimethylation of histone H3 arginine 2 (H3R2me2a), negatively regulates maintenance DNA methylation by impairing the recruitment of the Dnmt1-Uhrf1 complex to chromatin, thereby identifying a novel crosstalk between histone arginine methylation and DNA methylation. Moreover, I show that PRMT6 upregulation contributes to global DNA hypomethylation in cancer. Lastly, my work results in the identification of an intestine-specific Dnmt1 protein product that originates from a proteolytic cleavage event, which could shed light on the regulation of DNA methylation in intestinal stem cells (ISCs). In summary, the research work in this dissertation advances our understanding of the regulatory network that controls DNA methylation changes in normal developmental processes and pathological conditions.
Keywords
DNA methylation, Epigenetics, mouse embryonic stem cells, cancer, DNMT3A, DNMT3L, DNMT1, UHRF1, PRMT6, Histone arginine methylation
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