Date of Award

Spring 2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular Biophysics and Biochemistry

First Advisor

Bindra, Ranjit

Abstract

Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) is mutated frequently in gliomas and represents a potential target for cancer therapeutics development. ATRX is known to function as a histone chaperone that incorporates the histone variant, H3.3, into the genome. Studies have implicated ATRX in key DNA damage response (DDR) pathways, including non-homologous end joining (NHEJ), homologous recombination (HR), and replication stress response, but a distinct role for this protein in DNA repair has yet to be fully elucidated. To further investigate ATRX function in glioma, I created CRISPR knockout clones in multiple glioma cell lines. These cell lines were found to have DNA repair defects that indicated increased replication stress. I then determined that the immortalized astrocyte ATRX KO cell line is sensitive to PARP inhibitors. This sensitivity is due to an increase in replication stress identified through increased ATR activation. The DNA repair defect in these cells overlaps with a frequently co-occurring mutation in gliomas, IDH1 R132H, and so leads to equal sensitivity compared to either mutation alone. I also performed a CRISPR screen which highlighted the importance of the chromatin modifications made by ATRX and how knockout cells are more susceptible to chromatin instability. Taken together, these data reveal that ATRX may be used as a molecular marker for DDR defects and PARP inhibitor sensitivity, which is independent of IDH1/2 mutations. These data highlight the important role of common glioma-associated mutations in the regulation of DDR, and they highlight novel avenues for molecularly guided therapeutic intervention.

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