Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY, 11794, USA.
Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA.
DNA Repair (Amst). 2016 Jun;42:1-10. doi: 10.1016/j.dnarep.2016.03.013. Epub 2016 Apr 14.
DNA double-strand breaks (DSBs) are potentially lethal lesions repaired by two major pathways: homologous recombination (HR) and non-homologous end-joining (NHEJ). Homologous recombination preferentially reunites cognate broken ends. In contrast, non-homologous end-joining could ligate together any two ends, possibly generating dicentric or acentric fragments, leading to inviability. Here, we characterize the yeast NHEJ pathway in populations of pure G1 phase cells, where there is no possibility of repair using a homolog. We show that in G1 yeast cells, NHEJ is a highly effective repair pathway for gamma-ray induced breaks, even when many breaks are present. Pulsed-field gel analysis showed chromosome karyotypes following NHEJ repair of cells from populations with multiple breaks. The number of reciprocal translocations was surprisingly low, perhaps zero, suggesting that NHEJ preferentially re-ligates the "correct" broken ends instead of randomly-chosen ends. Although we do not know the mechanism, the preferential correct ligation is consistent with the idea that broken ends are continuously held together by protein-protein interactions or by larger scale chromatin structure.
DNA 双链断裂 (DSBs) 是潜在的致命损伤，可通过两种主要途径修复：同源重组 (HR) 和非同源末端连接 (NHEJ)。同源重组优先重组同源的断裂末端。相比之下，非同源末端连接可以将任意两个末端连接起来，可能产生双中心或无中心片段，导致细胞无法存活。在这里，我们在纯 G1 期细胞群体中表征了酵母 NHEJ 途径，在该群体中，不可能使用同源物进行修复。我们表明，在 G1 期酵母细胞中，NHEJ 是一种非常有效的γ射线诱导断裂修复途径，即使存在许多断裂。脉冲场凝胶分析显示了来自具有多个断裂的细胞群体的 NHEJ 修复后的染色体核型。相互易位的数量出人意料地低，也许为零，这表明 NHEJ 优先重新连接“正确”的断裂末端，而不是随机选择的末端。尽管我们不知道机制，但优先正确连接与这样的想法是一致的，即断裂末端通过蛋白质-蛋白质相互作用或更大规模的染色质结构持续保持在一起。
