Molecular analysis of cell cycle regulation by Ca^<2+>

研究了Ca^<2+>信号调控酿酒酵母G2/M细胞周期的分子机制。我们分离出与细胞周期调节相关的Ca^<2+>信号通路存在缺陷的突变体。这些突变体被划分为14个互补群。(1)对csz7突变体进行详细分析。scz7突变被鉴定为MCK1的一个等位基因，该等位基因编码真核生物中高度保守的GSK-3家族蛋白激酶。发现Mck1通过泛素-蛋白酶体途径参与Ca^<2+>-诱导的Hsl1 （Swe1的负调节因子）的失稳。我们进一步揭示了调控Hsl1丰度的详细机制。(2)对scz6突变体进行了详细分析。scz6突变被鉴定为PKC1的一个等位基因，该等位基因编码酵母中一种独特的蛋白激酶C。有趣的是，scz6突变抑制Ca^<2+>敏感生长和Ca^<2+>诱导的极化芽生长，但不影响G2细胞周期延迟。我们发现了Pkc1的新途径，其中Pkc1在调节SWE1和G1周期蛋白CLN1的转录中起重要作用，除了先前表征的激活Mpk1 MAP激酶途径的途径。转录因子Swi4参与了CLN1和SWE1的转录调控。对Scz5突变体进行了详细分析。scz5突变被鉴定为PDR5的一个等位基因，该基因编码一种与酵母多药耐药有关的ABC转运蛋白。Pdr5被认为与Ca^<2+>摄取有关。

We investigated molecular mechanism of G2/M cell cycle regulation by Ca^<2+> signal in Saccharomyces cerevisiae. We isolated mutants with a defect in the Ca^<2+> signaling pathway linked to cell cycle regulation. The mutants were classified to 14 complementation groups.(1) csz7 mutant was analyzed in detail. The scz7 mutation was identified as an allele of MCK1 that encodes a GSK-3 family protein kinase highly conserved among eukaryotes. It was found that Mck1 was involved in the Ca^<2+>-induced destabilization of Hsl1, Negative regulator of Swe1 through the ubiquitin-proteasome pathway. We further revealed the detailed mechanism by which Hsl1 abundance is regulated.(2) scz6 mutant was analyzed in detail. The scz6 mutation was identified as an allele of PKC1 that encodes a unique protein kinase C in the yeast. Interestingly, the scz6 mutation suppressed Ca^<2+> sensitive growth and Ca^<2+>-induced polarized bud growth, but not G2 cell cycle delay. We found a novel pathway of Pkc1, in which Pkc1 plays an important role in the regulation of the transcription of SWE1 And the G1 cyclin CLN1, in addition to the previously characterized pathway that activates the Mpk1 MAP kinase pathway. The transcription factor Swi4 was implicated in the transcriptional regulation of CLN1 and SWE1.scz5 mutant was analyzed in detail. The scz5 mutation was identified as an allele of PDR5 that encodes an ABC transporter implicated in multidrug resistance in the yeast. Pdr5 was suggested to be responsible for Ca^<2+> uptake.