Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY, 10032, USA.
Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY, 10032, USA.
Nat Commun. 2022 Jan 10;13(1):32. doi: 10.1038/s41467-021-27443-w.
Replication stress and abundant repetitive sequences have emerged as primary conditions underlying genomic instability in eukaryotes. To gain insight into the mechanism of recombination between repeated sequences in the context of replication stress, we used a prokaryotic Tus/Ter barrier designed to induce transient replication fork stalling near inverted repeats in the budding yeast genome. Our study reveals that the replication fork block stimulates a unique recombination pathway dependent on Rad51 strand invasion and Rad52-Rad59 strand annealing activities, Mph1/Rad5 fork remodelers, Mre11/Exo1/Dna2 resection machineries, Rad1-Rad10 nuclease and DNA polymerase δ. Furthermore, we show recombination at stalled replication forks is limited by the Srs2 helicase and Mus81-Mms4/Yen1 nucleases. Physical analysis of the replication-associated recombinants revealed that half are associated with an inversion of sequence between the repeats. Based on our extensive genetic characterization, we propose a model for recombination of closely linked repeats that can robustly generate chromosome rearrangements.
复制压力和丰富的重复序列已成为真核生物基因组不稳定性的主要条件。为了深入了解复制压力下重复序列之间重组的机制，我们使用了一种原核 Tus/Ter 屏障，旨在诱导芽殖酵母基因组中反向重复附近的瞬时复制叉停滞。我们的研究表明，复制叉阻断刺激了一种独特的重组途径，依赖于 Rad51 链入侵和 Rad52-Rad59 链退火活性、Mph1/Rad5 叉重塑酶、Mre11/Exo1/Dna2 切除机器、Rad1-Rad10 核酸内切酶和 DNA 聚合酶 δ。此外，我们还表明，停滞的复制叉处的重组受到 Srs2 解旋酶和 Mus81-Mms4/Yen1 核酸酶的限制。与复制相关的重组体的物理分析表明，其中一半与重复之间序列的倒位有关。基于我们广泛的遗传特征分析，我们提出了一个紧密连锁重复序列重组的模型，该模型可以有效地产生染色体重排。
