Parrish Jay Z, Yang Chonglin, Shen Binghui, Xue Ding
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
EMBO J. 2003 Jul 1;22(13):3451-60. doi: 10.1093/emboj/cdg320.
Oligonucleosomal fragmentation of chromosomes in dying cells is a hallmark of apoptosis. Little is known about how it is executed or what cellular components are involved. We show that crn-1, a Caenorhabditis elegans homologue of human flap endonuclease-1 (FEN-1) that is normally involved in DNA replication and repair, is also important for apoptosis. Reduction of crn-1 activity by RNA interference resulted in cell death phenotypes similar to those displayed by a mutant lacking the mitochondrial endonuclease CPS-6/endonuclease G. CRN-1 localizes to nuclei and can associate and cooperate with CPS-6 to promote stepwise DNA fragmentation, utilizing the endonuclease activity of CPS-6 and both the 5'-3' exonuclease activity and a previously uncharacterized gap-dependent endonuclease activity of CRN-1. Our results suggest that CRN-1/FEN-1 may play a critical role in switching the state of cells from DNA replication/repair to DNA degradation during apoptosis.
垂死细胞中染色体的寡核小体片段化是细胞凋亡的一个标志。目前对于其如何发生以及涉及哪些细胞成分知之甚少。我们发现,crn-1是人类瓣状核酸内切酶-1(FEN-1)在秀丽隐杆线虫中的同源物,通常参与DNA复制和修复,它对细胞凋亡也很重要。通过RNA干扰降低crn-1的活性会导致细胞死亡表型,类似于缺乏线粒体核酸内切酶CPS-6/核酸内切酶G的突变体所表现出的表型。CRN-1定位于细胞核,并且可以与CPS-6结合并协同作用,利用CPS-6的核酸内切酶活性以及CRN-1的5'-3'核酸外切酶活性和一种以前未被描述的间隙依赖性核酸内切酶活性来促进DNA的逐步片段化。我们的结果表明,CRN-1/FEN-1可能在细胞凋亡过程中将细胞状态从DNA复制/修复转变为DNA降解中起关键作用。