Perera David, Perez-Hidalgo Livia, Moens Peter B, Reini Kaarina, Lakin Nicholas, Syväoja Juhani E, San-Segundo Pedro A, Freire Raimundo
Unidad de Investigación, Hospital Universitario de Canarias, Ofra s/n, La Cuesta, 38320 Tenerife, Spain.
Mol Biol Cell. 2004 Apr;15(4):1568-79. doi: 10.1091/mbc.e03-06-0444. Epub 2004 Jan 12.
Mammalian TopBP1 is a BRCT domain-containing protein whose function in mitotic cells is linked to replication and DNA damage checkpoint. Here, we study its possible role during meiosis in mice. TopBP1 foci are abundant during early prophase I and localize mainly to histone gamma-H2AX-positive domains, where DNA double-strand breaks (required to initiate recombination) occur. Strikingly, TopBP1 showed a pattern almost identical to that of ATR, a PI3K-like kinase involved in mitotic DNA damage checkpoint. In the synapsis-defective Fkbp6(-/-) mouse, TopBP1 heavily stains unsynapsed regions of chromosomes. We also tested whether Schizosaccharomyces pombe Cut5 (the TopBP1 homologue) plays a role in the meiotic recombination checkpoint, like spRad3, the ATR homologue. Indeed, we found that a cut5 mutation suppresses the checkpoint-dependent meiotic delay of a meiotic recombination defective mutant, indicating a direct role of the Cut5 protein in the meiotic checkpoint. Our findings suggest that ATR and TopBP1 monitor meiotic recombination and are required for activation of the meiotic recombination checkpoint.
哺乳动物的TopBP1是一种含有BRCT结构域的蛋白质，其在有丝分裂细胞中的功能与复制和DNA损伤检查点相关。在此，我们研究它在小鼠减数分裂过程中可能发挥的作用。在减数分裂前期I早期，TopBP1位点大量存在，并且主要定位于组蛋白γ-H2AX阳性结构域，即发生DNA双链断裂（启动重组所必需）的区域。引人注目的是，TopBP1呈现出与ATR几乎相同的模式，ATR是一种参与有丝分裂DNA损伤检查点的类PI3K激酶。在突触缺陷的Fkbp6(-/-)小鼠中，TopBP1强烈染色染色体的未联会区域。我们还测试了粟酒裂殖酵母的Cut5（TopBP1的同源物）是否像ATR的同源物spRad3一样在减数分裂重组检查点中发挥作用。实际上，我们发现cut5突变抑制了减数分裂重组缺陷突变体的检查点依赖性减数分裂延迟，这表明Cut5蛋白在减数分裂检查点中具有直接作用。我们的研究结果表明，ATR和TopBP1监测减数分裂重组，并且是激活减数分裂重组检查点所必需的。
