Institut Jacques Monod, UMR7592, "Pathologies de la réplication de l'ADN", CNRS, Paris, France.
Biochemistry. 2011 Feb 15;50(6):932-44. doi: 10.1021/bi101583e. Epub 2011 Jan 20.
Single-stranded DNA binding (SSB) proteins are essential proteins of DNA metabolism. We characterized the binding of the bacteriophage T4 SSB, Escherichia coli SSB, human replication protein A (hRPA), and human hSSB1 proteins onto model miniforks and double-stranded-single-stranded (ds-ss) junctions exposing 3' or 5' ssDNA overhangs. T4 SSB proteins, E. coli SSB proteins, and hRPA have a different binding preference for the ss tail exposed on model miniforks and ds-ss junctions. The T4 SSB protein preferentially binds substrates with 5' ss tails, whereas the E. coli SSB protein and hRPA show a preference for substrates with 3' ss overhangs. When interacting with ds-ss junctions or miniforks, the T4 SSB protein, E. coli SSB protein, and hRPA can destabilize not only the ds part of a ds-ss junction but also the daughter ds arm of a minifork. The T4 SSB protein displays these unwinding activities in a polar manner. Taken together, our results position the SSB protein as a potential key player in the reversal of a stalled replication fork and in gap repair-mediated repetitive sequence expansion.
单链 DNA 结合（SSB）蛋白是 DNA 代谢的必需蛋白。我们研究了噬菌体 T4 SSB、大肠杆菌 SSB、人复制蛋白 A（hRPA）和人 hSSB1 蛋白与模型迷你分叉和双链单链（ds-ss）接头的结合情况，这些接头暴露了 3' 或 5' ssDNA 突出端。T4 SSB 蛋白、大肠杆菌 SSB 蛋白和 hRPA 对模型迷你分叉和 ds-ss 接头暴露的 ss 尾巴具有不同的结合偏好。T4 SSB 蛋白优先结合具有 5' ss 尾巴的底物，而大肠杆菌 SSB 蛋白和 hRPA 则优先结合具有 3' ss 突出端的底物。当与 ds-ss 接头或迷你分叉相互作用时，T4 SSB 蛋白、大肠杆菌 SSB 蛋白和 hRPA 不仅可以使 ds-ss 接头的 ds 部分失稳，还可以使迷你分叉的子双链臂失稳。T4 SSB 蛋白以极性方式显示这些解旋活性。总之，我们的研究结果将 SSB 蛋白定位为在停滞复制叉逆转和缺口修复介导的重复序列扩展中潜在的关键参与者。
