McGrew J T, Goetsch L, Byers B, Baum P
Department of Genetics, University of Washington, Seattle 98195.
Mol Biol Cell. 1992 Dec;3(12):1443-54. doi: 10.1091/mbc.3.12.1443.
Mutations in the ESP1 gene of Saccharomyces cerevisiae disrupt normal cell-cycle control and cause many cells in a mutant population to accumulate extra spindle pole bodies. To determine the stage at which the esp1 gene product becomes essential for normal cell-cycle progression, synchronous cultures of ESP1 mutant cells were exposed to the nonpermissive temperature for various periods of time. The mutant cells retained viability until the onset of mitosis, when their viability dropped markedly. Examination of these cells by fluorescence and electron microscopy showed the first detectable defect to be a structural failure in the spindle. Additionally, flow cytometric analysis of DNA content demonstrated that massive chromosome missegregation accompanied this failure of spindle function. Cytokinesis occurred despite the aberrant nuclear division, which often resulted in segregation of both spindle poles to the same cell. At later times, the missegregated spindle pole bodies entered a new cycle of duplication, thereby leading to the accumulation of extra spindle pole bodies within a single nucleus. The DNA sequence predicts a protein product similar to those of two other genes that are also required for nuclear division: the cut1 gene of Schizosaccharomyces pombe and the bimB gene of Aspergillus nidulans.
酿酒酵母ESP1基因的突变会破坏正常的细胞周期调控，导致突变群体中的许多细胞积累额外的纺锤体极体。为了确定esp1基因产物对正常细胞周期进程变得至关重要的阶段，将ESP1突变细胞的同步培养物在不同时间段暴露于非允许温度下。突变细胞在有丝分裂开始前保持活力，此时它们的活力显著下降。通过荧光显微镜和电子显微镜对这些细胞进行检查，发现第一个可检测到的缺陷是纺锤体的结构故障。此外，对DNA含量的流式细胞术分析表明，大量染色体错分离伴随着纺锤体功能的这种故障。尽管核分裂异常，细胞分裂仍会发生，这通常导致两个纺锤体极都分离到同一个细胞中。在后期，错分离的纺锤体极体进入新的复制周期，从而导致单个细胞核内积累额外的纺锤体极体。DNA序列预测一种蛋白质产物，类似于另外两个核分裂所需基因的产物：粟酒裂殖酵母的cut1基因和构巢曲霉的bimB基因。
