Text

theses

BRCA1-deficient cells exhibit increased genomic instability following DNA damaging treatments due to a defect in the homologous recombination (HR) DNA repair pathway. Here, we show that the Bloom Syndrome Protein, BLM, mediates the genomic instability observed in BRCA1-deficient cells by a mechanism that depends in part on its anti- recombinogenic activity. Ablation of BLM in BRCA1-deficient cells allows the HR repair pathway to be restored, leading to a partial rescue of the genomic instability and replication fork degradation that is present in BRCA1-deficient cells. The stable accumulation of RAD51 at DNA double-strand break sites is inhibited by BLM in BRCA1-deficient B cells. However, DNA end resection is not impacted by single or co- deletion of BRCA1 and BLM. Furthermore, cells co-deficient in BRCA1 and BLM display limited sensitivity to PARP inhibition. The rescue in HR and PARPi sensitivity phenotypes following deletion of BLM is only present in hypomorphic Brca1Δ11/Δ11 cells, and not in the RING domain deficient Brca1Δ2/Δ2 or nullizygous cells. Importantly, the helicase activity of BLM is required for its anti-recombinogenic function. Lastly, we demonstrate that BLM belongs to a class of anti-recombinases that limit the rate of HR. These results demonstrate that the anti-recombinogenic activity of BLM is of potentially great significance for regulating the balance of HR versus other error-prone repair pathways.

ETD_8274

Ph.D.

Includes bibliographical references

by Dharm S. Patel

doi:10.7282/T3280BRG

ETD doctoral

The author owns the copyright to this work.