Kim K, Biade S, Matsumoto Y
Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
J Biol Chem. 1998 Apr 10;273(15):8842-8. doi: 10.1074/jbc.273.15.8842.
Base excision repair can proceed in either one of two alternative pathways: a DNA polymerase beta-dependent pathway and a proliferating cell nuclear antigen (PCNA)-dependent pathway. Excision of an apurinic/apyrimidinic (AP) site by cutting the phosphate backbone on its 3' side following incision at its 5' side by AP endonuclease is a prerequisite to completion of these repair pathways. Using a reconstituted system with the proteins derived from Xenopus laevis, we found that flap endonuclease 1 (FEN1) was a factor responsible for the excision of a 5'-incised AP site in the PCNA-dependent pathway. In this pathway, DNA synthesis was not required for the action of FEN1 in the presence of PCNA and a replication factor C-containing fraction. The polymerase beta-dependent pathway could also use FEN1 for excision of the synthetic AP sites, which were not susceptible to beta-elimination. In this pathway, FEN1 was functional without PCNA and replication factor C but required the DNA synthesis, which led to a flap structure formation.
一种是DNA聚合酶β依赖性途径，另一种是增殖细胞核抗原（PCNA）依赖性途径。在脱嘌呤/脱嘧啶（AP）位点的5'侧由AP内切核酸酶切割后，通过切割其3'侧的磷酸主链来切除AP位点，这是完成这些修复途径的先决条件。使用从非洲爪蟾获得的蛋白质重建的系统，我们发现瓣状内切核酸酶1（FEN1）是在PCNA依赖性途径中负责切除5'切口AP位点的一个因子。在该途径中，在存在PCNA和含复制因子C的组分的情况下，FEN1的作用不需要DNA合成。聚合酶β依赖性途径也可以使用FEN1来切除不易被β消除的合成AP位点。在该途径中，FEN1在没有PCNA和复制因子C的情况下起作用，但需要DNA合成，这导致瓣状结构的形成。
