Description
- Abstract:
- DNA serves as a stable medium of genomic data but is also chemically reactive. These reactions may cause deleterious DNA damage undermining the integrity of the genome. It is therefore essential that DNA repair pathways correct any deleterious modifications. In eukaryotic organisms, DNA is packaged into chromatin. This packaging paradoxically shields DNA from damaging agents but also potentially DNA repair enzymes. Our studies investigate the molecular mechanisms that lead to mutational hotspots caused by DNA packaging. We utilized the basic unit of DNA packaging, the nucleosome core particle (NCP) as a model system for chromatin. The NCP is comprised of 145-147 base pairs of DNA wrapped around an octameric protein core consisting of two copies each of the four histone proteins: H2A, H2B, H3, and H4. Our unique global screening system utilizes novel chemical synthetic techniques to create a population of NCPs with DNA damage distributed in a various unique positions. We first investigated two different repair pathways, base excision repair (BER) and direct reversal repair (DRR), in the context of repairing alkylation damage in the NCP. Together the data shows the inability of either pathway to fully repair lesions occluded by packaging in the NCP. We next investigated how posttranslational modifications of the histones may alter the initiation of BER. These N-terminals tails are removed as part of epigenetic regulation and in response to DNA damage. We found that H2B and H3 tail removal induces structural alterations to the NCP that may both hinder and aid BER initiation. Finally, we investigated the ability of a damage sensor, ultraviolet DNA damage binding protein (UV-DDB), from the nucleotide excision repair pathway to stimulate BER in NCPs. Our preliminary results suggest UV-DDB may stimulate activity at occluded sites and dynamic areas of the NCP. Taken together, our studies further our understanding of the molecular mechanisms of mutational hotspots and several strategies that may be utilized to overcome the paradox of DNA packaging
- Notes:
- Thesis (Ph. D.)--Brown University, 2021
Citation
Caffrey, Paul,
"Accessing and Repairing DNA Damage in the Nucleosome Core Particle"
(2021).
Chemistry Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:zccuy8dv/
