Matsumoto T, Beach D
Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, New York 11724.
Cell. 1991 Jul 26;66(2):347-60. doi: 10.1016/0092-8674(91)90624-8.
A fission yeast mutant is described in which the onset of mitosis is uncoupled from the completion of DNA replication. pim1 (premature initiation of mitosis) cells can undergo mitotic chromosome condensation and mitotic spindle formation without completion of S phase and without the cdc25 mitotic inducer. The M phase kinase is required for pim1-induced mitosis and becomes activated. pim1 encodes a homolog of the human RCC1 nuclear protein. pim1 mutants are fully rescued by overexpression of spi1, a newly identified essential gene whose predicted product shares 81% identity with human TC4. spi1 and TC4 define a new subclass within the "ras-like" GTPase superfamily that is structurally distinct from the ras, rho, or sec4 families. Diploid yeast that carry one wild-type and one disrupted copy of spi1 have multiple satellite nuclei, and mitotic haploidization occurs at very high frequency. spi1 appears to interact with pim1 in the maintenance of a coordinated cell cycle.
描述了一种裂殖酵母突变体，其中有丝分裂的起始与DNA复制的完成相分离。pim1（有丝分裂过早起始）细胞在未完成S期且没有cdc25有丝分裂诱导剂的情况下，仍可进行有丝分裂染色体凝聚和有丝分裂纺锤体形成。M期激酶是pim1诱导的有丝分裂所必需的，并且会被激活。pim1编码人类RCC1核蛋白的一个同源物。通过过表达spi1可完全拯救pim1突变体，spi1是一个新鉴定的必需基因，其预测产物与人类TC4有81%的同一性。spi1和TC4在“类ras”GTP酶超家族中定义了一个新的亚类，其结构与ras、rho或sec4家族不同。携带一个野生型和一个spi1缺失拷贝的二倍体酵母有多个卫星核，并且有丝分裂单倍体化以非常高的频率发生。spi1似乎在维持协调的细胞周期中与pim1相互作用。
