Wells W A, Murray A W
Department of Physiology, University of California, San Francisco, 94143-0444, USA.
J Cell Biol. 1996 Apr;133(1):75-84. doi: 10.1083/jcb.133.1.75.
The spindle assembly checkpoint is the mechanism or set of mechanisms that prevents cells with defects in chromosome alignment or spindle assembly from passing through mitosis. We have investigated the effects of mini-chromosomes on this checkpoint in budding yeast by performing pedigree analysis. This method allowed us to observe the frequency and duration of cell cycle delays in individual cells. Short, centromeric linear mini-chromosomes, which have a low fidelity of segregation, cause frequent delays in mitosis. Their circular counterparts and longer linear mini-chromosomes, which segregate more efficiently, show a much lower frequency of mitotic delays, but these delays occur much more frequently in divisions where the mini-chromosome segregates to only one of the two daughter cells. Using a conditional centromere to increase the copy number of a circular mini-chromosome greatly increases the frequency of delayed divisions. In all cases the division delays are completely abolished by the mad mutants that inactivate the spindle assembly checkpoint, demonstrating that the Mad gene products are required to detect the subtle defects in chromosome behavior that have been observed to arrest higher eukaryotic cells in mitosis.
纺锤体组装检验点是一种机制或一组机制，可防止染色体排列或纺锤体组装存在缺陷的细胞进入有丝分裂。我们通过进行谱系分析，研究了微型染色体对芽殖酵母中该检验点的影响。这种方法使我们能够观察单个细胞中细胞周期延迟的频率和持续时间。具有低分离保真度的短着丝粒线性微型染色体，会频繁导致有丝分裂延迟。它们的环状对应物以及分离效率更高的较长线性微型染色体，有丝分裂延迟的频率要低得多，但这些延迟在微型染色体仅分离到两个子细胞之一的分裂中更频繁地发生。使用条件着丝粒增加环状微型染色体的拷贝数，会大大增加延迟分裂的频率。在所有情况下，纺锤体组装检验点失活的mad突变体可完全消除分裂延迟，这表明Mad基因产物是检测已观察到的会使高等真核细胞在有丝分裂中停滞的染色体行为细微缺陷所必需的。
