Gene conversion and deletion frequencies during double-strand break repair in human cells are controlled by the distance between direct repeats.
Gene conversion and deletion frequencies during double-strand break repair in human cells are controlled by the distance between direct repeats.
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人类细胞双链断裂修复期间的基因转换和缺失频率由同向重复之间的距离控制。
DOI：
10.1093/nar/gki295
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Nickoloff,JacA
中科院分区：
文献类型：
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作者：
Schildkraut,Ezra;Miller,CherylA;Nickoloff,JacA
同源重组修复DNA双链断裂，维持基因组的稳定性。连锁的直接重复序列之间的HR可以通过基因转换发生，而不需要维持总重复序列结构的相关交叉。或者，直接重复HR可以通过交叉基因转换或单链退火（SSA）发生，这两种方法都可以删除一个重复和重复之间的序列。先前对酵母和哺乳动物细胞中不同重复结构的研究揭示了不同的转换缺失率。在这里，我们发现控制这个比率的一个关键因素是重复序列之间的距离，转换频率随着距离从850到3800 bp的线性增加。缺失被认为主要是由SSA引起的，SSA涉及广泛的末端加工，以显示每个重复中的互补单链。结果可以用一个模型来解释，在这个模型中，链入侵导致的基因转化与SSA更有效地竞争，因为SSA需要更广泛的末端加工。我们假设重复序列之间的转录单位会抑制末端加工和SSA，从而增加转化的比例。然而，由3800 bp转录沉默或活性DNA分隔的直接重复序列的转换频率相同，表明末端加工和SSA不受转录的影响。
Homologous recombination (HR) repairs DNA double-strand breaks and maintains genome stability. HR between linked, direct repeats can occur by gene conversion without an associated crossover that maintains the gross repeat structure. Alternatively, direct repeat HR can occur by gene conversion with a crossover, or by single-strand annealing (SSA), both of which delete one repeat and the sequences between the repeats. Prior studies of different repeat structures in yeast and mammalian cells revealed disparate conversion:deletion ratios. Here, we show that a key factor controlling this ratio is the distance between the repeats, with conversion frequency increasing linearly with the distances from 850 to 3800 bp. Deletions are thought to arise primarily by SSA, which involves extensive end-processing to reveal complementary single-strands in each repeat. The results can be explained by a model in which strand-invasion leading to gene conversion competes more effectively with SSA as more extensive end-processing is required for SSA. We hypothesized that a transcription unit between repeats would inhibit end-processing and SSA, thereby increasing the fraction of conversions. However, conversion frequencies were identical for direct repeats separated by 3800 bp of transcriptionally silent or active DNA, indicating that end-processing and SSA are not affected by transcription.