Mechanisms of the signal transduction machinery in response to spontaneous DNA damage in human cells

重要的是要了解细胞表型，响应自发产生的DNA损伤，而没有外源性DNA损伤。我们已经从染色体不稳定性的角度研究了同源重组功能改变对细胞功能的影响。因为Rad51B和XRCC3在与Rad51一致的同源重组中起作用，我们使用了这些基因被敲除的人结肠癌细胞系。我们已经证明Rad51B通过稳定中心体来防止非整倍体的产生。我们之前已经证明XRCC3可以防止染色体复制。Cdt1稳定性增加和Cdc6在细胞核中积累增加被认为有助于XRCC3缺陷结肠癌细胞中的染色体复制。这种可能性在其他人类细胞中进行了研究。在Cdt1稳定的癌细胞中观察到由于XRCC3功能障碍引起的染色体复制，而在Cdt1不稳定的正常细胞中未明显观察到。因为我们先前表明RPA与XRCC3相关，所以通过RNA干扰在该系统中检查RPA的作用。EPA水平的降低阻止了XRCC3功能障碍诱导的染色体复制，表明EPA介导了XRCC3对染色体倍性的控制，以响应自发产生的DNA损伤。

It is important to understand cellular phenotypes that respond to spontaneously arising DNA damage without exogenous DNA damage. We have examined the effect of altered homologous recombination function on cell functions from the viewpoint of chromosome instability. Because Rad51B and XRCC3 play a role in homologous recombination in concert with Rad51, we used the human colon cancer cell line in which these genes were knocked out. We have shown that Rad51B prevents the generation of aneuploidy by stabilizing the centrosome. We previously showed that XRCC3 prevents chromosome duplication. Increased Cdt1 stability and increased accumulation of Cdc6 in the nucleus have been assumed to contribute to chromosome duplication in XRCC3 deficient colon cancer cells. This possibility was examined in other human cells. Chromosome duplication due to XRCC3 dysfunction was observed in cancer cells in which Cdt1 is stabilized, whereas it is not obviously observed in normal cells, in which Cdt1 is not stable. Because we previously showed that RPA is associated with XRCC3, the effect of RPA was examined in this system by RNA interference. Reduced levels of EPA prevented chromosome duplication induced by XRCC3 dysfunction, suggesting that EPA mediates the control of chromosome ploidy by XRCC3 in response to spontaneously arising DNA damage.