1H, 15N, and 13C resonance assignments for the N-terminal 20 kDa domain of the DNA single-strand break repair protein XRCC1.

Abstract

XRCC1 is a 633-residue protein necessary for the repair of single-strand DNA breaks in mammalian cells. The XRCC1 protein has three apparent domains that include the N-terminal 20 kDa domain, a central BRCT domain, and a C-terminal BRCT domain. Two intervening segments of the XRCC1 protein have not been classified. Chinese hamster ovary cell lines with mutations in the XRCC1 gene have characteristic DNA repair defects that include sensitivity to ionizing radiation, elevated levels of single-strand DNA breaks, and increased sister chromatid exchange (Thompson et al., 1990; Shen et al., 1998). Using methods that included affinity chromatography and yeast two-hybrid screening, the XRCC1 N-terminal domain and intact XRCC1 were shown to interact with mammalian β-Pol (Kubota et al., 1996). The C-terminal BRCT domain interacts with a BRCT domain in DNA ligase III. The central BRCT domain of XRCC1 has been shown to interact with a BRCT domain on PARP (Masson et al., 1998). Thus, the XRCC1 protein has been considered to be a scaffolding protein, necessary for formation of a βPol-XRCC1-DNA ligase III repair complex, and this complex may also interact with PARP. No structural information is available for the XRCC1 N-terminal domain. Here we report on the 1H, 15N, and 13C res∗To whom correspondence should be addressed. E-mail: gmullen@panda.uchc.edu Abbreviations: XRCC1, X-ray cross-complementing group 1 protein; β-Pol, DNA polymerase β; BER, base excision repair; BRCT, BRCA1 (breast cancer susceptibility protein) C-terminal domain; PARP, poly(ADP-ribose) polymerase; IPTG, isopropyl β-D-thiogalactopyranoside; AEBSF, 4-(2-aminoethyl)benzenesulfonylfluoride; DTT, dithiothreitol. onance assignments for the backbone and essentially all side chains within the XRCC1 20 kDa N-terminal domain.