The spindle midzone microtubule-associated proteins Ase1p and Cin8p affect the number and orientation of astral microtubules in Saccharomyces cerevisiae
The spindle midzone microtubule-associated proteins Ase1p and Cin8p affect the number and orientation of astral microtubules in Saccharomyces cerevisiae
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DOI：
10.4161/cc.6.10.4181
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发表时间：
2007-05-15
期刊：
影响因子：
4.3
通讯作者：
Cohen-Fix, Orna
中科院分区：
文献类型：
--
作者：
de Gramont, Armand;Barbour, Leslie;Cohen-Fix, Orna
芽殖酵母酿酒酵母的细胞核必须在有丝分裂过程中移动到芽颈，以便进行适当的 DNA 分离。这种运动由纺锤体和星体微管介导，并且依赖于微管相关运动蛋白产生的力。当出芽酵母细胞表达不可裂解的粘连蛋白亚基 Scc1-RRDD 时，姐妹染色单体的分离被阻断，从而阻止纺锤体伸长。因此，在 Scc1-RRDD 存在的情况下，核定位仅由通过星体微管作用的力介导。我们之前已经证明，在这些条件下，细胞与母细胞中的细胞核一起退出有丝分裂，并且细胞核的位置至少部分地由 FEAR 通路决定，该通路调节有丝分裂退出的各个方面。当 FEAR 通路失活时，表达 Scc1-RRDD 的细胞退出有丝分裂，细胞核位于子细胞中（称为“子代表型”）。为了找到参与核定位的其他蛋白质，我们筛选了一系列突变菌株，寻找在表达 Scc1-RRDD 时表现出子代表型的突变菌株。最突出的缺陷出现在 ase1 Delta 和 cin8 Delta 突变细胞中。 Ase1p 和 Cin8p 之前均被证明是细胞核并参与纺锤体功能。我们在此表明，ASE1 或 CIN8 的缺失会导致 SPB 分离缺陷，并导致星形微管数量异常及其在细胞内的方向发生变化。总而言之，这些结果表明，在出芽酵母中，Ase1p 和 Cin8p 通过星形微管依赖性机制影响核定位。
The nucleus of the budding yeast S. cerevisiae has to move to the bud neck during mitosis in order for proper DNA segregation to take place. This movement is mediated by spindle and astral microtubules, and it relies on forces generated by microtubule - associated motor proteins. When budding yeast cells express the non - cleavable cohesin subunit, Scc1-RRDD, sister chromatid separation is blocked, preventing the spindle from elongating. Thus, in the presence of Scc1-RRDD nuclear positioning is mediated solely by forces acting through astral microtubules. We have previously shown that under these conditions cells exit mitosis with the nucleus in the mother cells, and that the position of the nucleus is determined, at least in part, by the FEAR pathway, which regulates various aspects of mitotic exit. When the FEAR pathway is inactivated, cells expressing Scc1-RRDD exit mitosis with the nucleus in the daughter cells (referred to as a "daughterly phenotype"). In order to find additional proteins that participate in nuclear positioning, we screened a series of mutant strains for those that displayed a daughterly phenotype when Scc1-RRDD was expressed. The most prominent defects were seen in ase1 Delta and cin8 Delta mutant cells. Both Ase1p and Cin8p were previously shown to be nuclear and to be involved in spindle function. We show here that deletion of ASE1 or CIN8 causes a defect in SPB separation and leads to an abnormal number of astral microtubules and a change in their orientation within the cell. Taken together, these results suggest that in budding yeast Ase1p and Cin8p affect nuclear positioning through astral micro tubule - dependent mechanisms.