Nabeshima K, Nakagawa T, Straight A F, Murray A, Chikashige Y, Yamashita Y M, Hiraoka Y, Yanagida M
CREST Research Project, Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606, Japan.
Mol Biol Cell. 1998 Nov;9(11):3211-25. doi: 10.1091/mbc.9.11.3211.
In higher eukaryotic cells, the spindle forms along with chromosome condensation in mitotic prophase. In metaphase, chromosomes are aligned on the spindle with sister kinetochores facing toward the opposite poles. In anaphase A, sister chromatids separate from each other without spindle extension, whereas spindle elongation takes place during anaphase B. We have critically examined whether such mitotic stages also occur in a lower eukaryote, Schizosaccharomyces pombe. Using the green fluorescent protein tagging technique, early mitotic to late anaphase events were observed in living fission yeast cells. S. pombe has three phases in spindle dynamics, spindle formation (phase 1), constant spindle length (phase 2), and spindle extension (phase 3). Sister centromere separation (anaphase A) rapidly occurred at the end of phase 2. The centromere showed dynamic movements throughout phase 2 as it moved back and forth and was transiently split in two before its separation, suggesting that the centromere was positioned in a bioriented manner toward the poles at metaphase. Microtubule-associating Dis1 was required for the occurrence of constant spindle length and centromere movement in phase 2. Normal transition from phase 2 to 3 needed DNA topoisomerase II and Cut1 but not Cut14. The duration of each phase was highly dependent on temperature.
在高等真核细胞中，纺锤体在有丝分裂前期随着染色体浓缩而形成。在中期，染色体在纺锤体上排列，姐妹动粒朝向相反的两极。在后期A，姐妹染色单体彼此分离而纺锤体不延长，而纺锤体延长发生在后期B。我们严格检验了这样的有丝分裂阶段是否也发生在低等真核生物粟酒裂殖酵母中。使用绿色荧光蛋白标记技术，在活的裂殖酵母细胞中观察到了从有丝分裂早期到后期的事件。粟酒裂殖酵母在纺锤体动力学上有三个阶段，纺锤体形成（阶段1）、纺锤体长度恒定（阶段2）和纺锤体延长（阶段3）。姐妹着丝粒分离（后期A）在阶段2结束时迅速发生。着丝粒在整个阶段2都显示出动态运动，它前后移动并在分离前短暂地一分为二，这表明着丝粒在中期以双定向的方式朝向两极定位。微管相关蛋白Dis1是阶段2中纺锤体长度恒定和着丝粒运动发生所必需的。从阶段2到阶段3的正常转变需要DNA拓扑异构酶II和Cut1，但不需要Cut14。每个阶段的持续时间高度依赖于温度。
