近日，瑞典
据研究人员介绍，同源重组是准确修复双链DNA断裂（DSB）的关键。首先，RecBCD复合体将DSB的两端切除成3′单链DNA，并在上面组装成RecA丝。接着，该丝状物在姐妹染色体上找到同源的修复模板。
研究人员利用高通量微流控技术和荧光显微镜直接观察单细胞中DSB的修复情况。研究人员发现，在大肠杆菌中，分离的姐妹位点之间的DSB的修复在15±5分钟内完成（平均值±s.d.）。结果进一步表明，搜索需要不到9±3分钟（平均值±s.d），并且是由延伸到整个细胞的细长的、高度动态的RecA丝介导的。研究人员提出，RecA细丝的结构有效地降低了搜索维度。这个模型预测的搜索时间与测量结果一致，并得到了搜索时间不取决于细胞长度或DNA数量的观察结果的证实。考虑到RecA同源物的丰富性，研究人员认为这个模型在整个生物体中是广泛保守的。
附：英文原文
Title: RecA finds homologous DNA by reduced dimensionality search
Author: Wiktor, Jakub, Gynn, Arvid H., Leroy, Prune, Larsson, Jimmy, Coceano, Giovanna, Testa, Ilaria, Elf, Johan
Issue&Volume: 2021-09-01
Abstract: Homologous recombination is essential for the accurate repair of double-stranded DNA breaks (DSBs)1. Initially, the RecBCD complex2 resects the ends of the DSB into 3′ single-stranded DNA on which a RecA filament assembles3. Next, the filament locates the homologous repair template on the sister chromosome4. Here we directly visualize the repair of DSBs in single cells, using high-throughput microfluidics and fluorescence microscopy. We find that, in Escherichia coli, repair of DSBs between segregated sister loci is completed in 15±5min (mean ± s.d.) with minimal fitness loss. We further show that the search takes less than 9±3min (mean ± s.d) and is mediated by a thin, highly dynamic RecA filament that stretches throughout the cell. We propose that the architecture of the RecA filament effectively reduces search dimensionality. This model predicts a search time that is consistent with our measurement and is corroborated by the observation that the search time does not depend on the length of the cell or the amount of DNA. Given the abundance of RecA homologues5, we believe this model to be widely conserved across living organisms.
DOI: 10.1038/s41586-021-03877-6
Source: https://www.nature.com/articles/s41586-021-03877-6
Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
投稿链接：http://www.nature.com/authors/submit_manuscript.html
本期文章：《自然》：Online/在线发表
