title: Characterization of SIS1, a Saccharomyces cerevisiae homologue of bacterial dnaJ proteins.
abstract: The Saccharomyces cerevisiae SIS1 gene was identified as a high copy number suppressor of the slow growth phenotype of strains containing mutations in the SIT4 gene, which encodes a predicted serine/threonine protein phosphatase. The SIS1 protein is similar to bacterial dnaJ proteins in the amino-terminal third and carboxyl-terminal third of the proteins. In contrast, the middle third of SIS1 is not similar to dnaJ proteins. This region of SIS1 contains a glycine/methionine-rich region which, along with more amino-terminal sequences, is required for SIS1 to associate with a protein of apparent molecular mass of 40 kD. The SIS1 gene is essential. Strains limited for the SIS1 protein accumulate cells that appear blocked for migration of the nucleus from the mother cell into the daughter cell. In addition, many of the cells become very large and contain a large vacuole. The SIS1 protein is localized throughout the cell but is more concentrated at the nucleus. About one-fourth of the SIS1 protein is released from a nuclear fraction upon treatment with RNase. We also show that overexpression of YDJ1, another yeast protein with similarity to bacterial dnaJ proteins, can not substitute for SIS1.
authors.affiliation: Cold Spring Harbor Laboratory, New York 11724-2212.
authors.forename: M M
authors.initials: MM
authors.lastname: Luke
authors.forename: A
authors.initials: A
authors.lastname: Sutton
authors.forename: K T
authors.initials: KT
authors.lastname: Arndt
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002872:Chromosome Deletion; D004271:DNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D000939:Epitopes / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D005798:Genes, Bacterial; D005800:Genes, Fungal; D016153:Genes, Suppressor; D005838:Genotype; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D013347:Subcellular Fractions / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D004271:DNA, Fungal; C494635:DnaJ protein, E coli; D000939:Epitopes; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C070320:SIS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins