Weiss E, Winey M
Department of Molecular, Cellular, and Developmental Biology, University of Colorado-Boulder 80309-0347, USA.
J Cell Biol. 1996 Jan;132(1-2):111-23. doi: 10.1083/jcb.132.1.111.
M-phase checkpoints inhibit cell division when mitotic spindle function is perturbed. Here we show that the Saccharomyces cerevisiae MPS1 gene product, an essential protein kinase required for spindle pole body (SPB) duplication (Winey et al., 1991; Lauze et al., 1995), is also required for M-phase check-point function. In cdc31-2 and mps2-1 mutants, conditional failure of SPB duplication results in cell cycle arrest with high p34CDC28 kinase activity that depends on the presence of the wild-type MAD1 checkpoint gene, consistent with checkpoint arrest of mitosis. In contrast, mps1 mutant cells fail to duplicate their SPBs and do not arrest division at 37 degrees C, exhibiting a normal cycle of p34CDC28 kinase activity despite the presence of a monopolar spindle. Double mutant cdc31-2, mps1-1 cells also fail to arrest mitosis at 37 degrees C, despite having SPB structures similar to cdc31-2 single mutants as determined by EM analysis. Arrest of mitosis upon microtubule depolymerization by nocodazole is also conditionally absent in mps1 strains. This is observed in mps1 cells synchronized in S phase with hydroxyurea before exposure to nocodazole, indicating that failure of checkpoint function in mps1 cells is independent of SPB duplication failure. In contrast, hydroxyurea arrest and a number of other cdc mutant arrest phenotypes are unaffected by mps1 alleles. We propose that the essential MPS1 protein kinase functions both in SPB duplication and in a mitotic checkpoint monitoring spindle integrity.
当有丝分裂纺锤体功能受到干扰时，M期检查点会抑制细胞分裂。我们在此表明，酿酒酵母MPS1基因产物是纺锤极体（SPB）复制所必需的一种重要蛋白激酶（Winey等人，1991年；Lauze等人，1995年），它也是M期检查点功能所必需的。在cdc31-2和mps2-1突变体中，SPB复制的条件性失败导致细胞周期停滞，伴有高p34CDC28激酶活性，这依赖于野生型MAD1检查点基因的存在，与有丝分裂的检查点停滞一致。相比之下，mps1突变体细胞无法复制其SPB，并且在37℃时不会停止分裂，尽管存在单极纺锤体，仍表现出p34CDC28激酶活性的正常周期。双突变体cdc31-2、mps1-1细胞在37℃时也无法停止有丝分裂，尽管通过电子显微镜分析确定其SPB结构与cdc31-2单突变体相似。在mps1菌株中，用诺考达唑使微管解聚后，有丝分裂的停滞也有条件地缺失。这在先用羟基脲使处于S期的mps1细胞同步化，然后再暴露于诺考达唑的实验中观察到，表明mps1细胞中检查点功能的失败与SPB复制失败无关。相比之下，羟基脲停滞和许多其他cdc突变体停滞表型不受mps1等位基因的影响。我们提出，必需的MPS1蛋白激酶在SPB复制以及监测纺锤体完整性的有丝分裂检查点中均发挥作用。
