XRCC1 and cerebellar ataxia: For this purpose, we studied the wild-type XRCC1, polβ interaction mutants (V86R, R109A), the cancer-associated (P161L, R194W, R280H, R399Q, Y576S), and the cerebellar ataxia-related (K431N) variants of XRCC1 (Scheme S1).