Yuan Shyng-Shiou F, Chang Hsueh-Ling, Lee Eva Y-H P
Department of Obstetrics and Gynecology, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan, ROC.
Mutat Res. 2003 Apr 9;525(1-2):85-92. doi: 10.1016/s0027-5107(03)00009-5.
In eukaryotes, DNA double-strand breaks (DSBs) can be repaired by either non-homologous end-joining (NHEJ) or homologous recombination (HR) pathways. Rad50 protein is a component of the Rad50/NBS1/Mre11 nuclease complex that functions in both the NHEJ and recombinational repair of DNA DSBs. On the other hand, Rad51 protein, a homolog of bacterial RecA and a member of the Rad52 epistasis group, plays a crucial role exclusively in the recombinational repair pathway. We analyzed the effects of cell cycle progression and genetic background on the ionizing radiation (IR)-induced Rad51 and Rad50 repair focus formation. Herein, we demonstrated that IR-induced Rad51, but not Rad50, nuclear focus formation was cell cycle-dependent. Furthermore, IR-induced Rad51 focus formation was defective in AT and c-Abl(-/-) cells, but not wild type or NBS cells. A decreased and delayed formation of Rad51 foci-containing nuclei was observed in AT cells upon IR, whereas in c-Abl(-/-) cells a decreased but not delayed formation of Rad51 foci-containing nuclei was observed. In conclusion, effective and prompt IR-induced Rad51 focus formation is cell cycle-regulated and requires both ATM and c-Abl.
在真核生物中，DNA双链断裂（DSB）可通过非同源末端连接（NHEJ）或同源重组（HR）途径进行修复。Rad50蛋白是Rad50/NBS1/Mre11核酸酶复合物的一个组成部分，该复合物在DNA DSB的NHEJ和重组修复中均发挥作用。另一方面，Rad51蛋白是细菌RecA的同源物，属于Rad52上位性组的成员，仅在重组修复途径中起关键作用。我们分析了细胞周期进程和遗传背景对电离辐射（IR）诱导的Rad51和Rad50修复灶形成的影响。在此，我们证明了IR诱导的Rad51而非Rad50核灶形成是细胞周期依赖性的。此外，IR诱导的Rad51灶形成在共济失调毛细血管扩张症（AT）细胞和c-Abl基因敲除（-/-）细胞中存在缺陷，但在野生型或NBS细胞中则没有。IR照射后，在AT细胞中观察到含Rad51灶的细胞核形成减少且延迟，而在c-Abl（-/-）细胞中观察到含Rad51灶的细胞核形成减少但没有延迟。总之，IR诱导的有效且迅速的Rad51灶形成受细胞周期调控，并且需要ATM和c-Abl两者。
