Loeb J D, Schlenstedt G, Pellman D, Kornitzer D, Silver P A, Fink G R
Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142, USA.
Proc Natl Acad Sci U S A. 1995 Aug 15;92(17):7647-51. doi: 10.1073/pnas.92.17.7647.
The nuclear import system is highly conserved among eukaryotes. Here we report the effects of a conditional mutation in SRP1, which encodes a Saccharomyces cerevisiae homolog of the vertebrate nuclear import receptor importin. Importin was isolated as a factor required for the initial targeting step of a nuclear import substrate to the nuclear envelope in a mammalian in vitro assay. We show that yeast Srp1 is similarly required for protein import. In addition, Srp1 is also required for the execution of mitosis: we demonstrate that cells containing a conditional mutation of SRP1 arrest with a G2/M phenotype in a manner analogous to classic cdc mutants. This defect may be due to the failure of the mutant to degrade the mitotic cyclin Clb2 and other proteins required for mitosis. The requirement of a nuclear import receptor for cell cycle-regulated proteolysis implies that import of cell cycle regulators into the nucleus is critical for cell cycle progression.
核输入系统在真核生物中高度保守。在此，我们报告了SRP1条件性突变的影响，SRP1编码酿酒酵母中脊椎动物核输入受体输入蛋白的同源物。在哺乳动物体外试验中，输入蛋白被分离为核输入底物最初靶向核膜步骤所需的一个因子。我们表明酵母Srp1对于蛋白质输入同样是必需的。此外，Srp1对于有丝分裂的执行也是必需的：我们证明含有SRP1条件性突变的细胞以类似于经典cdc突变体的方式停滞在G2/M期表型。这种缺陷可能是由于突变体无法降解有丝分裂周期蛋白Clb2和有丝分裂所需的其他蛋白质。细胞周期调节性蛋白水解对核输入受体的需求意味着细胞周期调节因子进入细胞核对于细胞周期进程至关重要。
