Biomedical Sciences ETDs

Publication Date

Spring 5-10-2019


Eukaryotic genomes are assembled into a complex of DNA and proteins known as chromatin. The packaging of DNA into chromatin is the foundational strategy that cells use to both compress genomic DNA into nuclei and regulate access to its contents. The basic repeating subunit of chromatin is the nucleosome, composed of an octamer of two copies of each of the core histone proteins H2A, H2B, H3, and H4 around which 146 bp of DNA are tightly wrapped. While the compaction of genomes into chromatin offers cells significant advantages, it also presents serious challenges to fundamental processes that maintain genome integrity, including DNA repair and replication. Nucleosomes must be disrupted to allow access to damaged DNA by repair factors. Additionally, the millions of nucleosomes that package genomic DNA are displaced during DNA replication. After their displacement, nucleosomes must be faithfully restored to preserve proper chromatin compaction and regulation of access to DNA that underlie transcriptional programs and cellular identity. Thus, the processes that maintain genome and epigenome stability are intricately linked.

In the first aim of this dissertation, I examined the role of the conserved SWI/SNF ATP-dependent nucleosome remodeler in the repair of DNA double-strand breaks (DSBs) in yeast. I demonstrated that SWI/SNF facilitates the actions of the MRX complex at the DSB, including the eviction of KU, initiation of DNA end resection, recruitment of long-range resection factors, and activation of the DNA damage response. Furthermore, I showed that this activity of SWI/SNF is related to its role in the efficient eviction of nucleosomes near a DSB. This study contributes to an understanding of the roles of the clinically relevant SWI/SNF complex in mediating accurate repair of DSBs in the context of chromatin.

In the second aim, I examined the role of DNA Ligase I (Lig1) in coordinating chromatin assembly and maturation on newly replicated DNA in mammalian cells. I accumulated preliminary data demonstrating that Lig1 may influence the deposition of the linker histone H1 on DNA during replication, and that that Lig1 may also contribute to the recruitment of DNA methylation machinery. These combined studies provide novel information on two critical processes that maintain genetic and epigenetic stability in eukaryotes.


Chromatin, SWI/SNF, Double-Strand Break Repair, DNA Replication, DNA Ligase, Genome Stability

Document Type




Degree Name

Biomedical Sciences

Level of Degree


Department Name

Biomedical Sciences Graduate Program

First Committee Member (Chair)

Alan E Tomkinson, PhD

Second Committee Member

Mary Ann Osley, PhD

Third Committee Member

Diane S Lidke, PhD

Fourth Committee Member

David Y Lee, MD/PhD