title: Isolation and characterization of SYS genes from yeast, multicopy suppressors of the functional loss of the transport GTPase Ypt6p.
abstract: In Saccharomyces cerevisiae, the YPT6 gene encodes the homologue of the mammalian Rab6 protein found in the Golgi apparatus. Deletion of YPT6 in yeast produces a phenotype showing temperature-sensitive growth and partial missorting of the vacuolar enzyme, carboxypeptidase Y. To identify proteins that might: (1) interact with Ypt6p; or (2) act in the same pathway, we have isolated four multicopy suppressors, named SYS1, SYS2, SYS3 and SYS5, that can complement the temperature-sensitive growth phenotype of the ypt6 null mutant. On high expression, these genes are also able to partially suppress the missorting of carboxypeptidase Y.SYS2 on a multicopy plasmid suppresses in addition the temperature-sensitive phenotype of sec7-1, a mutant defective in transport between and from the Golgi compartment. Gene disruption of SYS1 and SYS2 did not result in significant growth defects. However, deletion of SYS1 and/or SYS2 in the ypt6 null mutant enhances defects in vacuolar protein sorting and in cell growth. Whereas protein secretion was not significantly affected in these mutants, the processing of alpha-factor precursor by the Kex2 protease was inhibited, suggesting a function of YPT6 and its null mutant suppressors in transport between the late Golgi and a prevacuolar, endosome-like compartment.
authors.affiliation: Max Planck Institute for Biophysical Chemistry, Department of Molecular Genetics, Göttingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tsukada
authors.forename: D
authors.initials: D
authors.lastname: Gallwitz
mesh_terms: D000595:Amino Acid Sequence; D002268:Carboxypeptidases / Q000502:physiology; D043402:Cathepsin A; D002455:Cell Division / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000502:physiology; D016153:Genes, Suppressor / Q000235:genetics* / Q000502:physiology; D006056:Golgi Apparatus / Q000235:genetics / Q000502:physiology; D000072235:Mating Factor; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D009024:Morphogenesis / Q000235:genetics; D009154:Mutation; D010455:Peptides / Q000235:genetics; D010675:Pheromones / Q000235:genetics; D043484:Proprotein Convertases; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013381:Subtilisins / Q000235:genetics / Q000502:physiology; D013696:Temperature; D014170:Transformation, Genetic; D014617:Vacuoles / Q000235:genetics / Q000502:physiology
chemical_list: D005656:Fungal Proteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor; D002268:Carboxypeptidases; D043402:Cathepsin A; D043484:Proprotein Convertases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins; C499307:YPT6 protein, S cerevisiae