title: The Gcn2 Regulator Yih1 Interacts with the Cyclin Dependent Kinase Cdc28 and Promotes Cell Cycle Progression through G2/M in Budding Yeast.
abstract: The Saccharomyces cerevisiae protein Yih1, when overexpressed, inhibits the eIF2 alpha kinase Gcn2 by competing for Gcn1 binding. However, deletion of YIH1 has no detectable effect on Gcn2 activity, suggesting that Yih1 is not a general inhibitor of Gcn2, and has no phenotypic defect identified so far. Thus, its physiological role is largely unknown. Here, we show that Yih1 is involved in the cell cycle. Yeast lacking Yih1 displays morphological patterns and DNA content indicative of a delay in the G2/M phases of the cell cycle, and this phenotype is independent of Gcn1 and Gcn2. Accordingly, the levels of phosphorylated eIF2α, which show a cell cycle-dependent fluctuation, are not altered in cells devoid of Yih1. We present several lines of evidence indicating that Yih1 is in a complex with Cdc28. Yih1 pulls down endogenous Cdc28 in vivo and this interaction is enhanced when Cdc28 is active, suggesting that Yih1 modulates the function of Cdc28 in specific stages of the cell cycle. We also demonstrate, by Bimolecular Fluorescence Complementation, that endogenous Yih1 and Cdc28 interact with each other, confirming Yih1 as a bona fide Cdc28 binding partner. Amino acid substitutions within helix H2 of the RWD domain of Yih1 enhance Yih1-Cdc28 association. Overexpression of this mutant, but not of wild type Yih1, leads to a phenotype similar to that of YIH1 deletion, supporting the view that Yih1 is involved through Cdc28 in the regulation of the cell cycle. We further show that IMPACT, the mammalian homologue of Yih1, interacts with CDK1, the mammalian counterpart of Cdc28, indicating that the involvement with the cell cycle is conserved. Together, these data provide insights into the cellular function of Yih1/IMPACT, and provide the basis for future studies on the role of this protein in the cell cycle.
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Silva
authors.affiliation: Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand.
authors.forename: Martina
authors.initials: M
authors.lastname: Dautel
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Bruno M
authors.initials: BM
authors.lastname: Di Genova
authors.affiliation: Department of Biochemistry and Molecular Biology, Upstate Medical University, State University of New York, Syracuse, New York, United States of America.
authors.forename: David C
authors.initials: DC
authors.lastname: Amberg
authors.affiliation: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Beatriz A
authors.initials: BA
authors.lastname: Castilho
authors.affiliation: Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Sattlegger
mesh_terms: D000818:Animals; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D019143:Evolution, Molecular; D059565:G2 Phase Cell Cycle Checkpoints; D055786:Gene Knockout Techniques; D051379:Mice; D008840:Microfilament Proteins / Q000502:physiology*; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D015852:Eukaryotic Initiation Factor-2; D008840:Microfilament Proteins; D029701:Saccharomyces cerevisiae Proteins; C488521:YIH1 protein, S cerevisiae; C512912:GCN2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae