Fission yeast WD-repeat protein Pop1 regulates genome ploidy through ubiquitin-proteasome-mediated degradation of the CDK inhibitor Rum1 and the S-phase initiator Cdc18
Fission yeast WD-repeat protein Pop1 regulates genome ploidy through ubiquitin-proteasome-mediated degradation of the CDK inhibitor Rum1 and the S-phase initiator Cdc18
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DOI：
10.1101/gad.11.12.1548
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发表时间：
1997-06-15
影响因子：
10.5
通讯作者：
Toda, T
中科院分区：
文献类型：
--
作者：
Kominami, K;Toda, T
在裂殖酵母中，基因组倍性的维持由至少两种机制控制。一个通过Cdc 2/Cdc 13激酶起作用，其中还涉及CDK抑制剂Rum 1，另一个通过S期调节剂Cdc 18起作用。通过筛选显示倍性增加的不育突变体，我们已经确定了一个新的基因，pop 1（+），在突变体成为多倍体。pop 1突变显示出与温度敏感的cdc 2或cdc 13突变的合成致死相互作用。在pop 1突变体中，Rum 1和Cdc 18蛋白质积累到高水平。pop 1突变体的高倍性表型依赖于rum 1（+）基因的存在，而Cdc 18的积累与rum 1无关。Pop 1蛋白的预测序列表明，它属于WD重复家族，与参与泛素依赖性途径的芽殖酵母Cdc 4具有最高同源性。与此观点一致，在26 S蛋白酶体的突变体中，Rum 1和Cdc 18的高分子量形式积累对应于这些蛋白的多聚泛素化。然而，在pop 1突变体中，没有检测到这些蛋白质的泛素化形式。最后，我们表明，Pop 1结合Cdc 18在体内。我们建议Pop 1作为Rum 1和Cdc 18的识别因子发挥作用，Rum 1和Cdc 18随后被泛素化并靶向26 S蛋白酶体进行降解。
In fission yeast, maintenance of genome ploidy is controlled by at least two mechanisms. One operates through the Cdc2/Cdc13 kinase, which also involves the CDK inhibitor Rum1, and the other through the S-phase regulator Cdc18. By screening for sterile mutants that show increased ploidy, we have identified a new gene, pop1(+), in mutants that become polyploid. The pop1 mutation shows a synthetic lethal interaction with the temperature-sensitive cdc2 or cdc13 mutation. In a pop1 mutant Rum1 and Cdc18 proteins become accumulated to high levels. The high ploidy phenotype in the pop1 mutant is dependent on the presence of the rum1(+) gene, whereas the accumulation of Cdc18 is independent of Rum1. The predicted sequence of the Pop1 protein indicates that it belongs to a WD-repeat family with highest homology to budding yeast Cdc4, which participates in the ubiquitin-dependent pathway. Consistent with this notion, in a mutant of the 26S proteasome, higher molecular weight forms of Rum1 and Cdc18 are accumulated corresponding to polyubiquitination of these proteins. In the pop1 mutant, however, no ubiquitinated forms of these proteins are detected. Finally we show that Pop1 binds Cdc18 in vivo. We propose that Pop1 functions as a recognition factor for Rum1 and Cdc18, which are subsequently ubiquitinated and targeted to the 26S proteasome for degradation.