Regulated nuclear accumulation of the yeast hsp70 Ssa4p in ethanol-stressed cells is mediated by the N-terminal domain, requires the nuclear carrier Nmd5p and protein kinase C.
Cytoplasmic proteins of the hsp70/hsc70 family redistribute in cells that have been exposed to stress. As such, the hsp70 Ssa4p of the budding yeast S. cerevisiae accumulates in nuclei when cells are treated with ethanol, whereas classical nuclear import is inhibited under these conditions. The N-terminal domain of Ssa4p, which is lacking a classical NLS, mediates nuclear accumulation upon ethanol exposure. Concentration of the Ssa4p N-terminal segment in nuclei is reversible, as the protein relocates to the cytoplasm when cells recover. Mutant analysis demonstrates that the small GTPase Gsp1p and GTPase-modulating factors are required to accumulate Ssa4p in nuclei upon ethanol stress. Moreover, we have identified the importin-beta family member Nmd5p as the nuclear carrier for Ssa4p. Ethanol treatment significantly increases the formation of import complexes containing Nmd5p and the N-terminal Ssa4p domain. Likewise, docking of the carrier Nmd5p at the nuclear pore is enhanced by ethanol. Furthermore, we show that the stressed-induced nuclear accumulation of Ssa4p depends on signaling through protein kinase C and requires sensors of the cell integrity pathway.
Physiology Department, McGill University, Montreal, PQ, Canada.
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D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000502:physiology; D000431:Ethanol / Q000494:pharmacology*; D020690:GTPase-Activating Proteins / Q000502:physiology; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D020662:Guanine Nucleotide Exchange Factors; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D028884:Karyopherins / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D046911:Macromolecular Substances; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology; D009687:Nuclear Proteins / Q000502:physiology; D018384:Oxidative Stress; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*
D004268:DNA-Binding Proteins; C080324:GSP1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D018840:HSP70 Heat-Shock Proteins; D028884:Karyopherins; D008164:Luminescent Proteins; D046911:Macromolecular Substances; C473023:NMD5 protein, S cerevisiae; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011500:Protein Synthesis Inhibitors; C060997:RNA1 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; C067050:SRM1 protein, S cerevisiae; C456269:SSA4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D000431:Ethanol; D003513:Cycloheximide; C490702:PKC1 protein, S cerevisiae; D011493:Protein Kinase C; D020559:Monomeric GTP-Binding Proteins