Fig. 2.

CTSS interacts with the BRCT domain of BRCA1 and inhibits BRCA1 protein expression. a Constructs of V5-CTSS and V5-C25A (active site of Cys25 mutated to Ala) were transiently transfected into Flag-BRCA1 transfected MCF7 cells, and cell extracts were subjected to immunoprecipitation (IP) and immunoblotting (IB). b Schematic presentation of BRCA1 domain, including RING, Rad51 interacting, and BRCT domains (upper). MCF7 cells were transfected with BRCA1 fragments (F1 to F6) encoding Myc with or without full-length V5-CTSS and analyzed by Western blotting (bottom). c Constructs of V5-CTSS and V5-C25A were transiently transfected into Flag-BRCT transfected MCF7 cells, and cell extracts were subjected to immunoprecipitation (IP) and immunoblotting (IB). d Schematic structure of BRCA1, BRCT, and BRCT deletion construct (ΔBRCT). MCF7 cells were transfected with WT-BRCA, BRCT with and without WT-CTSS, C25A and analyzed by Western blotting. e MCF7 cells were transfected with WT-BRCA and ΔBRCT constructs with and without WT-CTSS or sh-CTSS and analyzed by Western blotting. Protein levels were quantified using Image J software, and data are expressed as the fold change relative to the negative control