BRCA1 and ovarian cancer: USP15 is enrolled by the mediator of DNA damage checkpoint 1 (MDC1) to the DNA double-strand break to deubiquitinate BRCA1 associated with RING domain 1 (BARD1), enhancing the BARD1-HP1γ interaction and the BRCA1/BARD1 retention at the DNA double-strand break, as well as reducing the PARP inhibitor sensitivity in breast and ovarian cancer cells [54].