The CST Complex Mediates End Protection at Double-Strand Breaks and Promotes PARP Inhibitor Sensitivity in BRCA1-Deficient Cells
Selective elimination of BRCA1-deficient cells by inhibitors of poly(ADP-ribose) polymerase (PARP) is a prime example of the concept of synthetic lethality in cancer therapy. This interaction is counteracted by the restoration of BRCA1-independent homologous recombination through loss of factors such as 53BP1, RIF1, and REV7/MAD2L2, which inhibit end resection of DNA double-strand breaks (DSBs). To identify additional factors involved in this process, we performed CRISPR/SpCas9-based loss-of-function screens and selected for factors that confer PARP inhibitor (PARPi) resistance in BRCA1-deficient cells. Loss of members of the CTC1-STN1-TEN1 (CST) complex were found to cause PARPi resistance in BRCA1-deficient cells in vitro and in vivo. We show that CTC1 depletion results in the restoration of end resection and that the CST complex may act downstream of 53BP1/RIF1. These data suggest that, in addition to its role in protecting telomeres, the CST complex also contributes to protecting DSBs from end resection. Using CRISPR/SpCas9-based loss-of-function screens, Barazas et al. show that loss of the CTC1-STN1-TEN1 (CST) complex promotes PARP inhibitor resistance in BRCA1-deficient cells. Mechanistically, the CST complex maintains double-strand break end stability in addition to its role in protecting telomeric ends.
|BRCA1, breast cancer, CST complex, CTC1, DNA end resection, drug resistance, genetically engineered mouse model, PARP inhibitor, STN1, TEN1|
|Organisation||Department of Molecular Genetics|
Barazas, M, Annunziato, S. (Stefano), Pettitt, S.J. (Stephen J.), de Krijger, I. (Inge), Ghezraoui, H. (Hind), Roobol, S.J. (Stefan J.), … Rottenberg, S. (2018). The CST Complex Mediates End Protection at Double-Strand Breaks and Promotes PARP Inhibitor Sensitivity in BRCA1-Deficient Cells. Cell Reports. doi:10.1016/j.celrep.2018.04.046