Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan.
Mol Cell Biol. 2014 Apr;34(8):1389-97. doi: 10.1128/MCB.01704-13. Epub 2014 Jan 27.
The spindle assembly checkpoint (SAC) monitors defects in kinetochore-microtubule attachment or lack of tension at kinetochores and arrests cells at prometaphase. In fission yeast, the double mutant between pot1Δ and the helicase-dead point mutant of the RecQ helicase Rqh1 gene (rqh1-hd) accumulates Rad51-dependent recombination intermediates at telomeres and enters mitosis with those intermediates. Here, we found that SAC-dependent prometaphase arrest occurred more frequently in pot1Δ rqh1-hd double mutants than in rqh1-hd single mutants. SAC-dependent prometaphase arrest also occurred more frequently in rqh1-hd single mutants after cells were released from DNA replication block compared to the rqh1-hd single mutant in the absence of exogenous insult to the DNA. In both cases, Mad2 foci persisted longer than usual at kinetochores, suggesting a defect in kinetochore-microtubule attachment. In pot1Δ rqh1-hd double mutants and rqh1-hd single mutants released from DNA replication block, SAC-dependent prometaphase arrest was suppressed by the removal of the recombination or replication intermediates. Our results indicate that the accumulation of recombination or replication intermediates induces SAC-dependent prometaphase arrest, possibly by affecting kinetochore-microtubule attachment.
纺锤体组装检查点（SAC）监测着动粒-微管连接的缺陷或动粒缺乏张力，并将细胞阻滞在有丝分裂前期。在裂殖酵母中，pot1Δ 和 RecQ 解旋酶的无酶活性点突变体基因（rqh1-hd）的双突变体在端粒处积累 Rad51 依赖性重组中间体，并带着这些中间体进入有丝分裂。在这里，我们发现 pot1Δ rqh1-hd 双突变体中 SAC 依赖性有丝分裂前期阻滞的发生频率比 rqh1-hd 单突变体更高。与 DNA 未受到外源损伤的 rqh1-hd 单突变体相比，rqh1-hd 单突变体在从 DNA 复制阻断中释放后，SAC 依赖性有丝分裂前期阻滞的发生频率也更高。在这两种情况下，Mad2 焦点在动粒上的持续时间都比平时长，这表明动粒-微管连接存在缺陷。在从 DNA 复制阻断中释放的 pot1Δ rqh1-hd 双突变体和 rqh1-hd 单突变体中，通过去除重组或复制中间体，SAC 依赖性有丝分裂前期阻滞得到了抑制。我们的结果表明，重组或复制中间体的积累会诱导 SAC 依赖性有丝分裂前期阻滞，可能是通过影响动粒-微管连接。
