Cisplatin Affects the Conformation of Apo Form, not Holo Form, of BRCA1 RING Finger Domain and Confers Thermal Stability

The breast cancer suppressor protein 1 (BRCA1) has been shown to participate in genomic integrity maintenance Preclinical and clinical studies have recently revealed that the in of BRCA1 in cancer cells leads to chemosensitivity Approaching the BRCA1 RING protein as a potentially molecular target for a platinum-based drug might be of in in cancer therapy In the present study, the in vitro platination of the BRCA1 RING protein by the anticancer drug cisplatin was observed The protein contained a preformed structure in the apo form with structural changes and resistance to limited proteolysis after Zn2+ binding SIDS-PAGE and mass-spectrometric analyses revealed that cisplatin preferentially formed monofunctional and bifunctional BRCA1 adducts Tandem mass spectrometry (MS/MS) of the 656 29(2+) ion indicated that the ion arose from [Pt(NH3)(2)(OH)](+) bound to the BRCA1 peptide (ENNSPEHLK119)-E-111 The product-ion spectrum revealed the Pt-binding site on His117 Circular dichroism showed that the apo form, not hobo form, of BRCA1 underwent mole folded structural rearrangement upon cisplatin binding Cisplatin-bound protein exhibited an enhanced thermostability by 13 degrees, resulting from the favorably intermolecular cross-links driven by the free energy Our findings demonstrated the first conformational and thermal evidences for a direct binding of cisplatin to the BRCA1 RING domain and could raise a possibility of selectively targeted treatment of cancer with less toxicity or improved response to conventional regimens