Lacefield Soni, Magendantz Margaret, Solomon Frank
Department of Biology and Center for Cancer Research, M.I.T., Cambridge, Massachusetts 02139, USA.
Genetics. 2006 Jun;173(2):635-46. doi: 10.1534/genetics.105.055160. Epub 2006 Apr 2.
In budding yeast, the essential roles of microtubules include segregating chromosomes and positioning the nucleus during mitosis. Defects in these functions can lead to aneuploidy and cell death. To ensure proper mitotic spindle and cytoplasmic microtubule formation, the cell must maintain appropriate stoichiometries of alpha- and beta-tubulin, the basic subunits of microtubules. The experiments described here investigate the minimal levels of tubulin heterodimers needed for mitotic function. We have found a triple-mutant strain, pac10Delta plp1Delta yap4Delta, which has only 20% of wild-type tubulin heterodimer levels due to synthesis and folding defects. The anaphase spindles in these cells are approximately 64% the length of wild-type spindles. The mutant cells are viable and accurately segregate chromosomes in mitosis, but they do have specific defects in mitosis such as abnormal nuclear positioning. The results establish that cells with 20% of wild-type levels of tubulin heterodimers can perform essential cellular functions with a short spindle, but require higher tubulin heterodimer concentrations to attain normal spindle length and prevent mitotic defects.
在出芽酵母中，微管的重要作用包括在有丝分裂期间分离染色体和定位细胞核。这些功能的缺陷会导致非整倍体和细胞死亡。为确保有丝分裂纺锤体和细胞质微管的正常形成，细胞必须维持微管基本亚基α-微管蛋白和β-微管蛋白的适当化学计量。此处描述的实验研究了有丝分裂功能所需的微管蛋白异二聚体的最低水平。我们发现了一种三突变菌株pac10Delta plp1Delta yap4Delta，由于合成和折叠缺陷，其微管蛋白异二聚体水平仅为野生型的20%。这些细胞中的后期纺锤体长度约为野生型纺锤体的64%。突变细胞是有活力的，并且在有丝分裂中能准确分离染色体，但它们在有丝分裂中确实存在特定缺陷，如核定位异常。结果表明，微管蛋白异二聚体水平为野生型20%的细胞可以通过短纺锤体执行基本细胞功能，但需要更高的微管蛋白异二聚体浓度才能达到正常纺锤体长度并防止有丝分裂缺陷。
