The Arabidopsis BLAP75/Rmi1 homologue plays crucial roles in meiotic double-strand break repair.
The Arabidopsis BLAP75/Rmi1 homologue plays crucial roles in meiotic double-strand break repair.
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DOI：
10.1371/journal.pgen.1000309
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发表时间：
2008-12
期刊：
影响因子：
4.5
通讯作者：
Grelon M
中科院分区：
文献类型：
--
作者：
Chelysheva L;Vezon D;Belcram K;Gendrot G;Grelon M
在人类细胞和酿酒酵母中，BLAP 75/Rmi 1与BLM/Sgs 1和TopoIIIα/Top3共同作用，通过限制有利于NCO事件的交换（CO）形成来维持基因组稳定性，可能是通过溶解双霍利迪连接中间体（dHJ）。到目前为止，关于这些复合物参与减数分裂DNA修复的数据非常有限。在本文中，我们提出了第一个减数分裂研究的BLAP 75家族的成员，通过表征拟南芥同源。以.在拟南芥blap 75突变体中，启动减数分裂重组，并且重组进行直到形成二价样结构，即使在不存在ZMM蛋白的情况下。然而，早在中期I就可以检测到染色体断裂，并在后期I发生剧烈断裂，而没有观察到第二次减数分裂。通过遗传和免疫定位研究，我们发现这些缺陷反映了A。拟南芥BLAP 75在减数分裂双链断裂（DSB）修复中的作用-它在由RAD 51和相关蛋白介导的侵入步骤之后起作用，并且它是将减数分裂DSB修复到姐妹染色单体以及同源染色体上所必需的。总之，我们的研究结果首次表明，BLAP 75/Rmi 1是一个关键蛋白的减数分裂同源重组机制。以.在thaliana中，我们发现该蛋白对于同源染色体识别和突触是不可或缺的，但对于减数分裂DSB的修复是必需的。此外，在不存在BLAP 75的情况下，即使在不存在ZMM蛋白的情况下也可以发生二价形成，这表明在blap 75突变体中，存在重组中间体，其足够稳定以形成二价结构，即使当ZMM不存在时。DNA修复是细胞修复DNA损伤的过程。这种修复可以是交叉（CO），其中DNA分子进行主要交换，或非交叉（NCO）事件。真核细胞已经发展了几种机制，通过限制有利于NCO的CO事件的发生来维持营养发育期间的基因组稳定性。BLAP 75/Rmi 1、BLM/Sgs 1和TopoIIIα/Top3在一个复合物（BTB/RTR）中共同作用，已知是对抗CO形成的调控机制的关键组分。然而，CO/NCO调节被认为是非常不同的减数分裂过程中，因为同源染色体（父本和母本）克服至少一个CO/对。在本研究中，我们通过分析BTB/RTR复合体的一个成员：A. BLAP 75/Rmi 1的拟南芥同源物。我们首次表明，BLAP 75/Rmi 1也是减数分裂同源重组机制的关键蛋白。在拟南芥中，我们发现该蛋白是同源染色体识别和突触的必需蛋白，但对于减数分裂双链断裂的修复是必需的。此外，在不存在BLAP 75的情况下，即使在不存在CO的情况下也可以发生二价形成。
In human cells and in Saccharomyces cerevisiae, BLAP75/Rmi1 acts together with BLM/Sgs1 and TopoIIIα/Top3 to maintain genome stability by limiting crossover (CO) formation in favour of NCO events, probably through the dissolution of double Holliday junction intermediates (dHJ). So far, very limited data is available on the involvement of these complexes in meiotic DNA repair. In this paper, we present the first meiotic study of a member of the BLAP75 family through characterisation of the Arabidopsis thaliana homologue. In A. thaliana blap75 mutants, meiotic recombination is initiated, and recombination progresses until the formation of bivalent-like structures, even in the absence of ZMM proteins. However, chromosome fragmentation can be detected as soon as metaphase I and is drastic at anaphase I, while no second meiotic division is observed. Using genetic and imunolocalisation studies, we showed that these defects reflect a role of A. thaliana BLAP75 in meiotic double-strand break (DSB) repair—that it acts after the invasion step mediated by RAD51 and associated proteins and that it is necessary to repair meiotic DSBs onto sister chromatids as well as onto the homologous chromosome. In conclusion, our results show for the first time that BLAP75/Rmi1 is a key protein of the meiotic homologous recombination machinery. In A. thaliana, we found that this protein is dispensable for homologous chromosome recognition and synapsis but necessary for the repair of meiotic DSBs. Furthermore, in the absence of BLAP75, bivalent formation can happen even in the absence of ZMM proteins, showing that in blap75 mutants, recombination intermediates exist that are stable enough to form bivalent structures, even when ZMM are absent. Recombination is a process by which cells can repair DNA damage. Such repair can either be crossovers (CO), in which DNA molecules are submitted to major exchanges, or non-crossover (NCO) events. Eukaryotic cells have developed several mechanisms to maintain genome stability during vegetative development by limiting the occurrence of CO events in favour of NCO. BLAP75/Rmi1, BLM/Sgs1, and TopoIIIα/Top3 act together in a complex (BTB/RTR) known to be a crucial component of regulation mechanisms against CO formation. However, CO/NCO regulation is thought to be very different during meiosis since homologous chromosomes (paternal and maternal) overcome at least one CO/pair. In this study, we investigate the role of the BTB/RTR complex during meiotic recombination through the analysis of a function of one of its members: the A. thaliana homologue of BLAP75/Rmi1. We show for the first time that BLAP75/Rmi1 is also a key protein of the meiotic homologous recombination machinery. In Arabidopsis, we found that this protein is dispensable for homologous chromosome recognition and synapsis, but necessary for the repair of meiotic double-strand breaks. Furthermore, in the absence of BLAP75, bivalent formation can happen even in the absence of CO.
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