Kinoshita N, Ohkura H, Yanagida M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Cell. 1990 Oct 19;63(2):405-15. doi: 10.1016/0092-8674(90)90173-c.
The activities of type 1 protein phosphatase (PP1) and 2A (PP2A) have distinct, essential roles in cell cycle control. Two previously identified PP1 genes (dis2+ and sds21+) and two PP2A genes (ppa1+ and ppa2+), highly homologous to mammalian PP2A, have been isolated from fission yeast. Only double gene disruption of both PP2A genes results in lethality, as is the case for PP1 genes. By fractionating and assaying PPases in wild-type, various deletion, and point mutant strains, the decrease of PP1 or PP2A activity is shown to cause mitotic defects, exhibiting strikingly different cell cycle phenotypes: cold-sensitive mutations in the same amino acid lesion of PP1 and PP2A produce chromosome nondisjunction and premature mitosis, respectively. Consistently, PP1 and PP2A genes cannot be functionally substituted. Although the overall levels of PP1 and PP2A activities do not fluctuate during the cell cycle, subpopulations might be regulated.
1型蛋白磷酸酶（PP1）和2A（PP2A）的活性在细胞周期调控中具有独特的重要作用。从裂殖酵母中分离出了两个先前鉴定的与哺乳动物PP2A高度同源的PP1基因（dis2+和sds21+）以及两个PP2A基因（ppa1+和ppa2+）。与PP1基因一样，只有PP2A两个基因的双基因破坏才会导致致死性。通过对野生型、各种缺失和点突变菌株中的蛋白磷酸酶进行分级分离和测定，发现PP1或PP2A活性的降低会导致有丝分裂缺陷，表现出截然不同的细胞周期表型：PP1和PP2A相同氨基酸损伤处的冷敏感突变分别产生染色体不分离和有丝分裂过早。一致地，PP1和PP2A基因在功能上不能相互替代。虽然PP1和PP2A活性的总体水平在细胞周期中不波动，但亚群可能受到调控。
