title: Genetic interactions between KAR2 and SEC63, encoding eukaryotic homologues of DnaK and DnaJ in the endoplasmic reticulum.
abstract: KAR2 encodes the yeast homologue of mammalian BiP, the endoplasmic reticulum (ER) resident member of the HSP70 family. Kar2p has been shown to be required for the translocation of proteins across the ER membrane as well as nuclear fusion. Sec63, an ER integral membrane protein that shares homology with the Escherichia coli DnaJ protein, is also required for translocation. In this paper we describe several specific genetic interactions between these two proteins, Kar2p and Sec63p. First, temperature-sensitive mutations in KAR2 and SEC63 form synthetic lethal combinations. Second, dominant mutations in KAR2 are allele-specific suppressors for the temperature-sensitive growth and translocation defect of sec63-1. Third, the sec63-1, unlike other translocation defective mutations, results in the induction of KAR2 mRNA levels. Taken together, these genetic interactions suggest that Kar2p and Sec63p interact in vivo in a manner similar to that of the E. coli HSP70, DnaK, and DnaJ. We propose that the interaction between these two proteins is critical to their function in protein translocation.
authors.affiliation: Department of Molecular Biology, Princeton University, New Jersey 08544-1014.
authors.forename: M A
authors.initials: MA
authors.lastname: Scidmore
authors.forename: H H
authors.initials: HH
authors.lastname: Okamura
authors.forename: M D
authors.initials: MD
authors.lastname: Rose
mesh_terms: D003433:Crosses, Genetic; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins; D009154:Mutation / Q000235:genetics; D012331:RNA, Fungal / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics*; D011863:Radioimmunoassay; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic / Q000235:genetics; D013696:Temperature
chemical_list: D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C060153:KAR2 protein, yeast; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins