Interaction of yeast Rvs167 and Pho85 cyclin-dependent kinase complexes may link the cell cycle to the actin cytoskeleton

Background: PHO85 encodes the catalytic subunit of a cyclin-dependent kinase (Cdk) in budding yeast and functions in phosphate and glycogen metabolism. Pho85 associated with the G1 cyclins Pcl2 and Pcl2 is also required for cell cycle progression in the absence of the Cdc28 cyclins Cln1 and Cln2. Loss of Pcl1, Pcl2 and related Pho85 cyclins results in budding defects, suggesting that Pcl-Pho85 complexes function in cell morphogenesis early in the cell cycle; their precise role is not clear, however. Results: To identify targets for Pcl-Pho85 kinases, we performed yeast two-hybrid interaction screens using Pcl2 and the related cyclin Pcl9. We identified RVS167, a gene involved in endocytosis, organization of the actin cytoskeleton, and cell survival after starvation. Like rvs 167 Delta mutants, pho85 mutants or strains deleted for the Pcl1,2-type Pho85 cyclins showed abnormal cell morphology on starvation, sensitivity to salt, random budding in diploids, and defects in endocytosis and in the actin cytoskeleton. Overexpression of Rvs 167 in wild-type cells caused morphological abnormalities and growth arrest at high temperatures; these phenotypes were exacerbated by deleting PHO85. Rvs 167 has a Src homology 3 (SH3) domain and five potential Pho85 phosphorylation sites; recombinant Rvs167 was phosphorylated by the Pcl2-Pho85 kinase in vitro. Maximal phosphorylation of Rvs 167 in vivo required Pho85 and the Pcl1,2-type cyclins. Conclusions: Rvs167 interacts with Pho85 cyclins and is implicated as a target of Pho85 kinases in vive. Our results identify a connection between Cdks and the actin cytoskeleton; interaction of Rvs 167 and Pcl-Pho85 Cdks might contribute to actin cytoskeleton regulation in response to stresses such as starvation. (C) Current Biology Ltd ISSN 0960-9822.