Analysis of cyclins in the control of the cell cycle

细胞周期中的一项基本功能是将染色体平等地分裂为母细胞和子细胞。在发芽酵母中，母细胞中复制的核DNA通过单极运动向子芽迁移到母女交界处，同时伴随着芽的萌发和纺锤体的复制，然后在有丝分裂过程中，细胞核以双极方式拉出，在母细胞和子细胞中分裂成两个核叶。伴随着这种核运动，在细胞周期的有丝分裂过程中，不同的有丝分裂周期蛋白相继与CDC28激酶结合。为了探讨分裂前有丝分裂周期蛋白在细胞核运动中的作用，我们分析了有丝分裂周期蛋白对发芽酵母细胞核行为的影响。在酵母中过量生产脊椎动物细胞周期蛋白A1时，细胞核无法正确分裂，大部分染色体出现在子芽中，而不是分裂到母体和子体…更多的ER细胞。内源性细胞周期蛋白Clb3产生相同的表型，而Gl细胞周期蛋白Cln2不产生相同的表型。同时，有丝分裂的短纺锤体和两个SPBS进入子芽，胞质纺锤体在母细胞中表现出异常的形态，而在子细胞中则表现出异常的形态。这种表型是通过产生一个坚不可摧的细胞周期蛋白突变体来观察到的，而不是通过一个不能激活CDC28激酶的突变细胞周期蛋白来观察的。这些结果提示，有丝分裂周期蛋白Cyclin A和Clb3引起的核异常运动可能是纺锤体功能改变的结果。细胞分裂前的细胞核运动和纺锤体转变过程可能受细胞周期蛋白A介导的CDC28激酶及其细胞周期蛋白降解的调控。我们分离了能够挽救细胞周期蛋白A表达导致的酵母生长停滞的突变体，并鉴定了与细胞周期蛋白A相互作用的4个基因，CDC28、DEAD1、YDJ1是泛素相关新基因CDC28的新等位基因。我们需要在细胞周期调控的分子水平上对这些因素进行更多的分析。较少

One essential function in the cell cycle is the equal division of chromosomes into the mother and the daughter cell. In the budding yeast Saccharomyces cerevisiae, nuclear DNA replicated in the mother cell migrates to the mother-daughter junction by uni-polar movement towards the daughter bud in concert with bud emergence and spindle duplication, and then the nucleus is pulled by bi-polar mode and divided to two nuclear lobes in the mother and the daughter cell during mitosis. Accompanied by this nuclear movement, different mitotic cyclins are successively associated with Cdc28 kinase during mitosis in the cell cycle. To address the function of mitotic cyclins in nuclear movement prior to division, we analyzed the effects of mitotic cyclins on behavior of the nucleus in budding yeast.On overproducing vertebrate cyclin Al in the yeast, the nucleus failed to divide correctly and the majority of chromosomes were found in the daughter bud, instead of dividing into the mother and the daught … More er cells. Endogenous mitotic cyclin Clb3 produced the same phenotypes, whereas Gl cyclin Cln2 did not. Concomitantly, short mitotic spindles and two SPBs entered into the daughter bud, and cytoplasmic spindles showed an aberrant morphology in the mother cell rather than in the daughter. This phenotype was observed by producing an indestructible cyclin mutant, but not by a mutated cyclin unable to activate Cdc28 kinase. These results suggset that the aberrant nuclear movement induced by mitotic cyclin cyclin A,as well as Clb3, may result from an altered spindle function. The process of nuclear movement and the spindle transition prior to division might be regulated by cyclin A-mediated Cdc28 kinase and its cyclin degradation.We isolated the mutants that can rescue the growth arrest caused by cyclin A expression in the budding yeast, and identified the four genes, which can interact which cyclin A-Cdc28 complex, a new allele of CDC28, DEAD1, YDJ1, a novel ubiquitin-related gene. We need more analysis of these factors at the molecular level in cell cycle regulation. Less