TOPBP1 and breast cancer: In contrast to HTATSF1/Wt and HTATSF1/S748D, HTATSF1/S748A mutation could not efficiently rescue HTATSF1 depletion-induced defects, upon cisplatin (Fig. 3, D and E) and irradiation (Fig. S3, C and D) treatment, including TOPBP1 recruitment and RAD51 loading at γH2AX-marked damaged chromatin (Fig. S3E) in EdU-labeled S-phase breast cancer cells.