Measday V, Moore L, Retnakaran R, Lee J, Donoviel M, Neiman A M, Andrews B
Department of Molecular and Medical Genetics, University of Toronto, Canada.
Mol Cell Biol. 1997 Mar;17(3):1212-23. doi: 10.1128/MCB.17.3.1212.
In budding yeast, entry into the mitotic cell cycle, or Start, requires the Cdc28 cyclin-dependent kinase (Cdk) and one of its three associated G1 cyclins, Cln1, Cln2, or Cln3. In addition, two other G1 cyclins, Pcl1 and Pcl2, associate with a second Cdk, Pho85, to contribute to Start. Although Pho85 is not essential for viability, Pcl1,2-Pho85 kinase complexes become essential for Start in the absence of Cln1,2-Cdc28 kinases. In addition, Pho85 interacts with a third cyclin, Pho80, to regulate acid phosphatase gene expression. Other cellular roles for Pho85 cyclin-Cdk complexes are suggested by the multiple phenotypes associated with deletion of PHO85, in addition to Start defects and deregulated acid phosphatase gene expression. Strains with pho80, pcl1, and pcl2 deletions show only a subset of the pho85 mutant phenotypes, suggesting the existence of additional Pho85 cyclins (Pcls). We used two-hybrid screening and database searching to identify seven additional cyclin-related genes that may interact with Pho85. We found that all of the new genes encode proteins that interacted with Pho85 in an affinity chromatography assay. One of these genes, CLG1, was previously suggested to encode a cyclin, based on the protein's sequence homology to Pcl1 and Pcl2. We have named the other genes PCL5, PCL6, PCL7, PCL8, PCL9, and PCL10. On the basis of sequence similarities, the PCLs can be divided into two subfamilies: the Pcl1,2-like subfamily and the Pho80-like subfamily. We found that deletion of members of the Pcl1,2 class of genes resulted in pronounced morphological abnormalities. In addition, we found that expression of one member of the Pcl1,2 subfamily, PCL9, is cell cycle regulated and is decreased in cells arrested in G1 by pheromone treatment. Our studies suggest that Pho85 associates with multiple cyclins and that subsets of cyclins may direct Pho85 to perform distinct roles in cell growth and division.
在芽殖酵母中，进入有丝分裂细胞周期（即起始点）需要Cdc28细胞周期蛋白依赖性激酶（Cdk）及其三种相关的G1细胞周期蛋白之一，即Cln1、Cln2或Cln3。此外，另外两种G1细胞周期蛋白Pcl1和Pcl2与第二种Cdk即Pho85结合，对起始点起作用。虽然Pho85对细胞存活并非必需，但在缺乏Cln1,2 - Cdc28激酶的情况下，Pcl1,2 - Pho85激酶复合物对起始点变得至关重要。此外，Pho85与第三种细胞周期蛋白Pho80相互作用，以调节酸性磷酸酶基因的表达。除了起始点缺陷和酸性磷酸酶基因表达失调外，与PHO85缺失相关的多种表型暗示了Pho85细胞周期蛋白 - Cdk复合物的其他细胞功能。缺失pho80、pcl1和pcl2的菌株仅表现出pho85突变体表型的一部分，这表明存在其他Pho85细胞周期蛋白（Pcls）。我们利用双杂交筛选和数据库搜索来鉴定另外七个可能与Pho85相互作用的细胞周期蛋白相关基因。我们发现所有新基因编码的蛋白质在亲和层析分析中都与Pho85相互作用。其中一个基因CLG1，基于其蛋白质与Pcl1和Pcl2的序列同源性，之前被认为编码一种细胞周期蛋白。我们将其他基因命名为PCL5、PCL6、PCL7、PCL8、PCL9和PCLl0。基于序列相似性，PCLs可分为两个亚家族：Pcl1,2样亚家族和Pho80样亚家族。我们发现缺失Pcl1,2类基因的成员会导致明显的形态异常。此外，我们发现Pcl1,2亚家族的一个成员PCL9的表达受细胞周期调控，并且在通过信息素处理而停滞在G1期的细胞中表达降低。我们的研究表明，Pho85与多种细胞周期蛋白结合，并且细胞周期蛋白的子集可能指导Pho85在细胞生长和分裂中发挥不同的作用。
