Lanker S, Valdivieso M H, Wittenberg C
Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
Science. 1996 Mar 15;271(5255):1597-601. doi: 10.1126/science.271.5255.1597.
Cyclins regulate the major cell cycle transitions in eukaryotes through association with cyclin-dependent protein kinases (CDKs). In yeast, G1 cyclins are essential, rate-limiting activators of cell cycle initiation. G1-specific accumulation of one G1 cyclin, Cln2, results from periodic gene expression coupled with rapid protein turnover. Site-directed mutagenesis of CLN2 revealed that its phosphorylation provides a signal that promotes rapid degradation. Cln2 phosphorylation is dependent on the Cdc28 protein kinase, the CDK that it activates. These findings suggest that Cln2 is rendered self-limiting by virtue of its ability to activate its cognate CDK subunit.
细胞周期蛋白通过与细胞周期蛋白依赖性蛋白激酶（CDK）结合来调控真核生物中的主要细胞周期转换。在酵母中，G1期细胞周期蛋白是细胞周期起始所必需的限速激活因子。一种G1期细胞周期蛋白Cln2在G1期的特异性积累源于周期性基因表达以及快速的蛋白质周转。对CLN2进行定点诱变表明，其磷酸化提供了一个促进快速降解的信号。Cln2的磷酸化依赖于Cdc28蛋白激酶，即它所激活的CDK。这些发现表明，Cln2因其激活同源CDK亚基的能力而具有自我限制作用。
