Tange Yoshie, Niwa Osami
Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818, Japan.
Genetics. 2008 Jun;179(2):785-92. doi: 10.1534/genetics.107.081695. Epub 2008 May 27.
The core proteins of the spindle assembly checkpoint (SAC), Mads, Bubs, and Mps1, first identified in the budding yeast, are thought to be functionally and structurally conserved through evolution. We found that fission yeast Bub3 is dispensable for SAC, as bub3 null mutants blocked mitotic progression when spindle formation was disrupted. Consistently, the bub3 mutation only weakly affected the stability of minichromosome Ch16 compared with other SAC mutants. Fission yeast Rae1 has sequence homology with Bub3. The bub3 rae1 double mutant and rae1 single mutant did not have defective SAC, suggesting that these genes do not have overlapping roles for SAC. Observations of living cells revealed that the duration of the mitotic prometaphase/metaphase was longer in the bub3 mutant and was Mad2 dependent. Further, the bub3 mutant was defective in sister centromere association during metaphase. Together, these findings suggest that fission yeast Bub3 is required for normal spindle dynamics, but not for SAC.
纺锤体组装检查点（SAC）的核心蛋白Mads、Bubs和Mps1最初是在芽殖酵母中发现的，人们认为它们在进化过程中功能和结构保守。我们发现，裂殖酵母中的Bub3对于SAC是可有可无的，因为当纺锤体形成被破坏时，bub3基因敲除突变体阻断了有丝分裂进程。同样，与其他SAC突变体相比，bub3突变对小染色体Ch16的稳定性影响较弱。裂殖酵母Rae1与Bub3具有序列同源性。bub3 rae1双突变体和rae1单突变体的SAC没有缺陷，这表明这些基因在SAC中没有重叠作用。对活细胞的观察表明，有丝分裂前中期/中期的持续时间在bub3突变体中更长，并且依赖于Mad2。此外，bub3突变体在中期姐妹着丝粒关联方面存在缺陷。总之，这些发现表明裂殖酵母Bub3是正常纺锤体动力学所必需的，但不是SAC所必需的。
