Article
Author: Raught, Brian ; Khosraviani, Negin ; Algouneh, Arash ; Mateo, Francesca ; Guturi, Kiran Kumar Naidu ; Earnshaw, Rebecca ; Arrowsmith, Cheryl ; Miller, Joshua ; Yerlici, V Talya ; Lapierre, Mariah ; Alaoui-Jamali, Moulay ; Patel, Parasvi S ; Krishnan, Rehna ; Reynolds, John J ; Mekhail, Karim ; Nixon, Kevin C J ; Ho, Brandon ; Gautreau, Brandon ; Penn, Adam ; Saad, Amine ; Masson, Jean-Yves ; Stewart, Grant S ; Shili, Duan ; Seitova, Alma ; Hakem, Razqallah ; Pujana, Miguel A ; St-Germain, Jonathan ; El Ghamrasni, Samah ; Hao, Jun ; Hakem, Anne ; Hande, M Prakash ; Sanchez, Otto ; Brown, Grant W
Breast cancer linked with BRCA1/2 mutations commonly recur and resist current therapies, including PARP inhibitors. Given the lack of effective targeted therapies for BRCA1-mutant cancers, we sought to identify novel targets to selectively kill these cancers. Here, we report that loss of RNF8 significantly protects Brca1-mutant mice against mammary tumorigenesis. RNF8 deficiency in human BRCA1-mutant breast cancer cells was found to promote R-loop accumulation and replication fork instability, leading to increased DNA damage, senescence, and synthetic lethality. Mechanistically, RNF8 interacts with XRN2, which is crucial for transcription termination and R-loop resolution. We report that RNF8 ubiquitylates XRN2 to facilitate its recruitment to R-loop-prone genomic loci and that RNF8 deficiency in BRCA1-mutant breast cancer cells decreases XRN2 occupancy at R-loop-prone sites, thereby promoting R-loop accumulation, transcription-replication collisions, excessive genomic instability, and cancer cell death. Collectively, our work identifies a synthetic lethal interaction between RNF8 and BRCA1, which is mediated by a pathological accumulation of R-loops.