Survival pathways supporting BRCA1 function

Anthony, Elizabeth ORCID: 0000-0002-5927-7472 (2024). Survival pathways supporting BRCA1 function. University of Birmingham. Ph.D.

Preview

Anthony2024PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (16MB) | Preview

Abstract

The \(\underline{B}\)reast \(\underline{ca}\)ncer susceptibility protein \(\underline{1}\) (BRCA1) is a tumour suppressor protein that functions in the DNA damage response and in replication. In DNA double-strand break repair BRCA1 functions within the pathway homologous recombination, mainly in the regulation of DNA resection. Its roles in replication, including the protection of stalled replication forks and the suppression of single-stranded DNA (ssDNA) post-replicative gaps, are poorly understood. BRCA1 forms a heterodimeric complex with BRCA1 associated RING domain 1 (BARD1), forming an active E3 ubiquitin ligase, the cellular roles of which remain controversial. A method of further understanding the functional role(s) of BRCA1 is to investigate the pathways supporting cell survival when some of those functions are disabled.

A synthetic lethal interaction between DNA polymerase θ (Polθ) loss in BRCA1- mutated cells has been identified, yet the mechanisms underlying this relationship remain to be fully elucidated. In this thesis, we have determined that BRCA-RAD51 interactions suppress cell sensitivity to Polθ loss using Brca1\(^{C61G/C61G}\) 53bp1\(^{-/-}\) mouse embryonic fibroblasts (MEFs) as our Brca1-mutated model. In addition, we find that RAD52 underlies the synthetic lethal relationship between Brca1/53bp1 deficiencies and Polθ depletion. We identified that Polθ limits RAD52-mediated suppression of ssDNA gap fill-in during G2/M.

We also investigated a potential ligase-defective murine allele, Bard1\(^{R93E/R93E}\). Bard1\(^{R93E/R93E}\) cells are proficient in homologous recombination yet form ssDNA gaps behind replication forks. We found that the Bard1\(^{R93E/R93E}\) cells exhibited sensitivity to the loss of ubiquitin-specific protease 1 (USP1). These Bard1-mutant cells have provided preliminary findings surrounding the role of USP1 in DNA damage tolerance (DDT) mechanisms in our cells. Overall, the findings in this thesis increase our understanding of survival pathways supporting BRCA1 function.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):