Funabiki H, Kumada K, Yanagida M
Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Japan.
EMBO J. 1996 Dec 2;15(23):6617-28.
Fission yeast Schizosaccharomyces pombe temperature-sensitive (ts) cut1 mutants fail to separate sister chromatids in anaphase but the cells continue to divide, leading to bisection of the undivided nucleus (the cut phenotype). If cytokinesis is blocked, replication continues, forming a giant nucleus with polyploid chromosomes. We show here that the phenotype of ts cut2-364 is highly similar to that of cut1 and that the functions of the gene products of cut1+ and cut2+ are closely interrelated. The cut1+ and cut2+ genes are essential for viability and interact genetically. Cut1 protein concentrates along the short spindle in metaphase as does Cut2. Cut1 (approximately 200 kDa) and Cut2 (42 kDa) associate, as shown by immunoprecipitation, and co-sediment as large complexes (30 and 40S) in sucrose gradient centrifugation. Their behavior in the cell cycle is strikingly different, however: Cut2 is degraded in anaphase by the same proteolytic machinery used for the destruction of cyclin B, whereas Cut1 exists throughout the cell cycle. The essential function of the Cut1-Cut2 complex which ensures sister chromatid separation may be regulated by Cut2 proteolysis. The C-terminal region of Cut1 is evolutionarily conserved and similar to that of budding yeast Esp1, filamentous fungi BimB and a human protein.
裂殖酵母粟酒裂殖酵母温度敏感型（ts）cut1突变体在后期无法分离姐妹染色单体，但细胞仍继续分裂，导致未分裂的细胞核一分为二（cut表型）。如果胞质分裂受阻，复制继续进行，形成具有多倍体染色体的巨大细胞核。我们在此表明，ts cut2 - 364的表型与cut1高度相似，并且cut1 +和cut2 +基因产物的功能密切相关。cut1 +和cut2 +基因对于细胞存活至关重要且在遗传上相互作用。在中期，Cut1蛋白与Cut2一样沿着短纺锤体聚集。如免疫沉淀所示，Cut1（约200 kDa）和Cut2（42 kDa）相互结合，并在蔗糖梯度离心中作为大复合物（30和40S）共同沉降。然而，它们在细胞周期中的行为显著不同：Cut2在后期通过用于破坏细胞周期蛋白B的相同蛋白水解机制被降解，而Cut1在整个细胞周期中都存在。确保姐妹染色单体分离的Cut1 - Cut2复合物的基本功能可能受Cut2蛋白水解调节。Cut1的C末端区域在进化上是保守的，并且与芽殖酵母Esp1、丝状真菌BimB和一种人类蛋白的C末端区域相似。
