Marintchev A, Mullen M A, Maciejewski M W, Pan B, Gryk M R, Mullen G P
Department of Biochemistry, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06032, USA.
Nat Struct Biol. 1999 Sep;6(9):884-93. doi: 10.1038/12347.
XRCC1 functions in the repair of single-strand DNA breaks in mammalian cells and forms a repair complex with beta-Pol, ligase III and PARP. Here we describe the NMR solution structure of the XRCC1 N-terminal domain (XRCC1 NTD). The structural core is a beta-sandwich with beta-strands connected by loops, three helices and two short two-stranded beta-sheets at each connection side. We show, for the first time, that the XRCC1 NTD specifically binds single-strand break DNA (gapped and nicked). We also show that the XRCC1 NTD binds a gapped DNA-beta-Pol complex. The DNA binding and beta-Pol binding surfaces were mapped by NMR and found to be well suited for interaction with single-strand gap DNA containing a 90 degrees bend, and for simultaneously making contacts with the palm-thumb of beta-Pol in a ternary complex. The findings suggest a mechanism for preferential binding of the XRCC1 NTD to flexible single-strand break DNA.
XRCC1在哺乳动物细胞单链DNA断裂修复中发挥作用，并与β-聚合酶、连接酶III和聚（ADP-核糖）聚合酶（PARP）形成修复复合物。在此，我们描述了XRCC1 N端结构域（XRCC1 NTD）的核磁共振溶液结构。其结构核心是一个β-折叠片层，β-链通过环连接，在每个连接侧有三个螺旋和两个短的双链β-折叠片层。我们首次表明，XRCC1 NTD特异性结合单链断裂DNA（缺口和切口）。我们还表明，XRCC1 NTD结合缺口DNA-β-聚合酶复合物。通过核磁共振绘制了DNA结合和β-聚合酶结合表面，发现它们非常适合与含有90度弯曲的单链缺口DNA相互作用，并在三元复合物中同时与β-聚合酶的手掌-拇指区域接触。这些发现提示了XRCC1 NTD优先结合柔性单链断裂DNA的机制。
