Dzantiev Leonid, Constantin Nicoleta, Genschel Jochen, Iyer Ravi R, Burgers Peter M, Modrich Paul
Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA.
Mol Cell. 2004 Jul 2;15(1):31-41. doi: 10.1016/j.molcel.2004.06.016.
Mismatch-provoked excision directed by a strand break located 3' or 5' to the mispair has been reconstituted using purified human proteins. While MutSalpha, EXOI, and RPA are sufficient to support hydrolysis directed by a 5' strand break, 3' directed excision also requires MutLalpha, PCNA, and RFC. EXOI interacts with PCNA. RFC and PCNA suppress EXOI-mediated 5' to 3' hydrolysis when the nick that directs excision is located 3' to the mispair and activate 3' to 5' excision, which is dependent on loaded PCNA and apparently mediated by a cryptic EXOI 3' to 5' hydrolytic function. By contrast, RFC and PCNA have only a limited effect on 5' to 3' excision directed by a 5' strand break.
利用纯化的人类蛋白质，已重建了由位于错配位点3'或5'端的链断裂引发的错配诱导切除。虽然MutSα、EXO1和RPA足以支持由5'链断裂引导的水解，但3'端引导的切除还需要MutLα、PCNA和RFC。EXO1与PCNA相互作用。当引导切除的切口位于错配位点的3'端时，RFC和PCNA会抑制EXO1介导的5'至3'水解，并激活3'至5'切除，这依赖于负载的PCNA，且显然由EXO1潜在的3'至5'水解功能介导。相比之下，RFC和PCNA对由5'链断裂引导的5'至3'切除只有有限的影响。
