Schultz Niklas, Lopez Elena, Saleh-Gohari Nasrollah, Helleday Thomas
Department of Genetic and Cellular Toxicology, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
Nucleic Acids Res. 2003 Sep 1;31(17):4959-64. doi: 10.1093/nar/gkg703.
Cells with non-functional poly(ADP-ribose) polymerase (PARP-1) show increased levels of sister chromatid exchange, suggesting a hyper recombination phenotype in these cells. To further investigate the involvement of PARP-1 in homologous recombination (HR) we investigated how PARP-1 affects nuclear HR sites (Rad51 foci) and HR repair of an endonuclease-induced DNA double-strand break (DSB). Several proteins involved in HR localise to Rad51 foci and HR-deficient cells fail to form Rad51 foci in response to DNA damage. Here, we show that PARP-1 mainly does not localise to Rad51 foci and that Rad51 foci form in PARP-1-/- cells, also in response to hydroxyurea. Furthermore, we show that homology directed repair following induction of a site-specific DSB is normal in PARP-1-inhibited cells. In contrast, inhibition or loss of PARP-1 increases spontaneous Rad51 foci formation, confirming a hyper recombination phenotype in these cells. Our data suggest that PARP-1 controls DNA damage recognised by HR and that it is not involved in executing HR as such.
聚（ADP-核糖）聚合酶1（PARP-1）功能缺失的细胞显示姐妹染色单体交换水平升高，表明这些细胞具有高重组表型。为了进一步研究PARP-1在同源重组（HR）中的作用，我们研究了PARP-1如何影响核HR位点（Rad51灶点）以及核酸内切酶诱导的DNA双链断裂（DSB）的HR修复。几种参与HR的蛋白质定位于Rad51灶点，而HR缺陷细胞在DNA损伤时无法形成Rad51灶点。在此，我们表明PARP-1主要不定位于Rad51灶点，并且在PARP-1基因敲除细胞中也能形成Rad51灶点，同样是对羟基脲的反应。此外，我们表明在PARP-1抑制的细胞中，位点特异性DSB诱导后的同源定向修复是正常的。相反，PARP-1的抑制或缺失会增加自发的Rad51灶点形成，证实了这些细胞中的高重组表型。我们的数据表明，PARP-1控制由HR识别的DNA损伤，并且它本身不参与执行HR。
