Efficient Single-Strand Break Repair Requires Binding to Both Poly(ADP-Ribose) and DNA by the Central BRCT Domain of XRCC1

？ Interaction of XRCC1 with PAR and DNA are both mediated by the central BRCT domain ？ Interaction with PAR and DNA occurs through non-overlapping binding surfaces ？ Mutational disruption of DNA binding to XRCC1 impairs recruitment to DNA damage ？ Disruption of DNA binding by XRCC1 impairs repair of DNA single-strand break