Characterization of the novel human AP endonuclease and poly-ADP-ribosyl transferase.

Cyr基序首先在修复蛋白PALF(ALPF)中被发现，并在DNA代谢和DNA修复的各种蛋白质中发现。我们新发现了含有CyR基序的蛋白质：果蝇CG1218及其人类同源基因C4orf27，它含有一个保守的DUF2228结构域。我们假设这些蛋白质具有与DNA代谢相关的功能。我们分离了CG1218和人C4orf27的cDNA，并对其进行了鉴定。我们发现：1)CG1218蛋白聚集在DNA损伤部位，人C4orf27蛋白与PARP1形成异源二聚体，并聚集在DNA损伤部位；2)CG1218和C4orf27具有抗碱性位点的核酸内切酶/外切核酸酶活性。3)使用siRNA抑制C4orf27的表达为细胞提供了对MMS的敏感性，MMS产生甲基化碱基导致单链断裂。这些数据表明，DUF2228蛋白CG1218-PA和C4orf27在DNA碱基损伤修复和单链断裂中发挥重要作用。

The CYR motif was first identified in the repair protein, PALF (ALPF), and found in various proteins of DNA metabolism and DNA repair. We newly identified the CYR motif containing proteins, Drosophila CG1218 and its human ortholog C4orf27, which contained a conserved DUF2228 domain. We hypothesized that these proteins have DNA metabolism related functions. We isolated cDNA of CG1218 and human C4orf27, and characterized these proteins. Here we show that; 1) a CG1218 protein accumulates at DNA damaged site and human C4orf27 protein forms a hetero dimmer with PARP1 and accumulates at DNA damaged site 2) CG1218 and C4orf27 possess endo/exonuclease activities against abasic site. 3) Suppression of the expression of C4orf27 using siRNA provided the cells with sensitivity to MMS, which produces methylated bases leading to single-strand breaks. These data suggest that DUF2228 protein CG1218-PA and C4orf27 play important roles in the repair of DNA base damage and single-strand breaks.