The function of X-ray cross complementing group 1 protein (XRCC1), a scaffold that binds to DNA repair enzymes involved in single-strand break and base excision repair, requires that it be recruited to sites of damaged DNA. However, structural insights into this recruitment are currently limited. Sequence analysis of the first unstructured linker domain of XRCC1 identifies a segment consistent with a possible REV1 interacting region (X1RIR) motif. The X1RIR motif is present in translesion polymerases that can be recruited to the pol /REV1 DNA repair complex via a specific interaction with the REV1 C-terminal domain. NMR and fluorescence titration studies were performed on XRCC1-derived peptides containing this putative RIR motif in order to evaluate the binding affinity for the REV1 C-terminal domain. These studies demonstrate an interaction of the XRCC1-derived peptide with the human REV1 C-terminal domain characterized by dissociation constants in the low micromolar range. Ligand competition studies comparing the XRCC1 RIR peptide with previously studied RIR peptides were found to be inconsistent with the NMR based Kd values. These discrepancies were resolved using a fluorescence assay for which the RIR–REV1 system is particularly well suited. The structure of a REV1-XRCC1 peptide complex was determined by using NOE restraints to dock the unlabeled XRCC1 peptide with a labeled REV1 C-terminal domain. The structure is generally homologous with previously determined complexes with the pol κ and pol η RIR peptides, although the helical segment in XRCC1 is shorter than was observed in these cases. These studies suggest the possible involvement of XRCC1 and its associated repair factors in post replication repair.

中文翻译：

---

XRCC1 与 REV1 C 端域的相互作用表明在复制后修复中起作用。

X 射线交叉互补组 1 蛋白 (XRCC1) 是一种支架，可与参与单链断裂和碱基切除修复的 DNA 修复酶结合，其功能需要将其募集到受损 DNA 的位点。然而，目前对这种招聘的结构性见解是有限的。XRCC1 的第一个非结构化接头域的序列分析确定了与可能的 REV1 相互作用区域 (X1RIR) 基序一致的片段。X1RIR 基序存在于跨损伤聚合酶中，可通过与 REV1 C 端域的特定相互作用被募集到 pol /REV1 DNA 修复复合物。对含有该假定 RIR 基序的 XRCC1 衍生肽进行了核磁共振和荧光滴定研究，以评估对 REV1 C 端结构域的结合亲和力。这些研究证明了 XRCC1 衍生肽与人类 REV1 C 末端结构域的相互作用，其特征在于低微摩尔范围内的解离常数。发现将 XRCC1 RIR 肽与先前研究的 RIR 肽进行比较的配体竞争研究与基于 NMR 的 Kd 值不一致。使用 RIR-REV1 系统特别适合的荧光分析解决了这些差异。REV1-XRCC1 肽复合物的结构是通过使用 NOE 约束将未标记的 XRCC1 肽与标记的 REV1 C 端域对接来确定的。该结构通常与先前确定的与 pol κ 和 pol η RIR 肽的复合物同源，尽管 XRCC1 中的螺旋段比在这些情况下观察到的要短。