XRCC1 and cancer: For DNA ligase IIIα/XRCC1 interaction, when compared with wild-type XRCC1 (Fig. 2B, KD: 50.4 nM), the binding constant values for the cancer-associated variants P161L, R194W, R280H, R399Q, and Y576S showed similar interaction patterns as the KD values were in the range of 30 to 50 nM (Fig. S4, A–E).