Examining the association between BRCA1 and topoisomerase I in cancer cells in response to camptothecin treatment
Godley IV, Frederick Augustus
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DNA topoisomerase I (TopoI) is an essential enzyme involved in the relief of DNA supercoiling during replication. TopoI plays important role in various DNA events, however the recognition that it is the target of anticancer drug camptothecins (CPTs) led to the rapid growth in this field. CPTs inhibit TopoI during S phase and cause double stranded DNA lesions in rapidly dividing cells. This class of drug is used extensively in oncology clinical settings worldwide. However, resistance to this type of therapy has been found in approximately 70% of the patient population. Current evidence supports that degradation of TopoI by the Ubiquitin Proteasomal Pathway (UPP), and consequent compensation by Topoisomerase II expression may be involved in imparting drug resistance, but this mechanism requires much greater understanding. Protein-protein interaction studies have indicated that, BRCA1 is the E3 ligase for TopoI ubiquitination in response to CPT. BRCA1 impaired cells fail to ubiquitinate and degrade TopoI and are sensitive to CPTs. It is important to note that triple negative breast cancer patients have impaired BRCA1 function, higher mutation rate and/or a lower expression of BRCA1. The Bharti lab has shown that TopoI associates with BRCA1. Our work attempts to elucidate the nature of the interaction between BRCA1 and TopoI in the hope of better understanding the mechanism of resistance to camptothecin therapy in TNBC.