Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Nucleic Acids Res. 2022 Jan 25;50(2):899-914. doi: 10.1093/nar/gkab1253.
During meiosis, DNA double-strand breaks (DSBs) are formed at high frequency at special chromosomal sites, called DSB hotspots, to generate crossovers that aid proper chromosome segregation. Multiple chromosomal features affect hotspot formation. In the fission yeast S. pombe the linear element proteins Rec25, Rec27 and Mug20 are hotspot determinants - they bind hotspots with high specificity and are necessary for nearly all DSBs at hotspots. To assess whether they are also sufficient for hotspot determination, we localized each linear element protein to a novel chromosomal site (ade6 with lacO substitutions) by fusion to the Escherichia coli LacI repressor. The Mug20-LacI plus lacO combination, but not the two separate lac elements, produced a strong ade6 DSB hotspot, comparable to strong endogenous DSB hotspots. This hotspot had unexpectedly low ade6 recombinant frequency and negligible DSB hotspot competition, although like endogenous hotspots it manifested DSB interference. We infer that linear element proteins must be properly placed by endogenous functions to impose hotspot competition and proper partner choice for DSB repair. Our results support and expand our previously proposed DSB hotspot-clustering model for local control of meiotic recombination.
在减数分裂过程中，DNA 双链断裂（DSB）高频地在特殊的染色体位点形成，这些位点被称为 DSB 热点，以产生有助于正确染色体分离的交叉。多个染色体特征影响热点的形成。在裂殖酵母 S. pombe 中，线性元件蛋白 Rec25、Rec27 和 Mug20 是热点决定因素-它们与热点具有高度特异性结合，并且几乎是所有热点处 DSB 的必要条件。为了评估它们是否足以决定热点，我们通过与大肠杆菌 LacI 阻遏物融合，将每种线性元件蛋白定位到一个新的染色体位点（ade6 带有 lacO 取代）。Mug20-LacI 加 lacO 组合，但不是两个单独的 lac 元件，产生了一个强的 ade6 DSB 热点，与强的内源性 DSB 热点相当。尽管这个热点表现出 DSB 干扰，但它出人意料地具有低的 ade6 重组频率和可忽略不计的 DSB 热点竞争。我们推断，线性元件蛋白必须通过内源性功能被正确地放置，以施加 DSB 修复的热点竞争和适当的伙伴选择。我们的结果支持并扩展了我们之前提出的 DSB 热点聚类模型，用于对减数分裂重组的局部控制。
