Abstract
The endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway eliminates aberrant proteins from the ER. The key role of Cdc48p-Ufd1p-Npl4p is indicated by impaired ERAD in Saccharomyces cerevisiae with mutations in any of this complex's genes. We identified SSZ1 in genetic screens for cdc48-10 suppressors and show that it upregulates Cdc48p via the pleiotropic drug resistance (PDR) network. A pSSZ1 plasmid restored impaired ERAD-M of 6myc-Hmg2 in cdc48-10, ufd1-2, and npl4-1, while SSZ1 deletion had no effect. Ssz1p activates Pdr1p, the PDR master regulator. Indeed, plasmids of PDR1 or its target gene RPN4 increased cdc48-10p levels and restored ERAD-M in cdc48-10. Rpn4p regulates transcription of proteasome subunits and CDC48, thus RPN4 deletion abolished ERAD. However, the diminished proteasome level in Deltarpn4 was sufficient for degrading a cytosolic substrate, whereas the impaired ERAD-M was the result of diminished Cdc48p and was restored by expression of pCDC48. The corrected ERAD-M in the hypomorphic strains of the Cdc48 partners ufd1-2 and npl4-1 by the pCDC48 plasmid, and in cdc48-10 cells by the pcdc48-10 plasmid, combined with the finding that neither pSSZ1 nor pcdc48-10 restored ERAD-L of CPY*-HA, support our conclusion that Ssz1p suppressing effects is brought about by upregulating Cdc48p.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphatases / genetics
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Adenosine Triphosphatases / metabolism*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Drug Resistance, Fungal / physiology
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Endoplasmic Reticulum / genetics
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Endoplasmic Reticulum / metabolism*
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Gene Deletion
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Gene Expression Regulation, Fungal / physiology*
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HSP70 Heat-Shock Proteins / genetics
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HSP70 Heat-Shock Proteins / metabolism*
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Nucleocytoplasmic Transport Proteins / genetics
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Nucleocytoplasmic Transport Proteins / metabolism*
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Proteasome Endopeptidase Complex / biosynthesis
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Proteasome Endopeptidase Complex / genetics
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Transcription, Genetic / physiology
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Up-Regulation / physiology
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Valosin Containing Protein
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Vesicular Transport Proteins / genetics
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Vesicular Transport Proteins / metabolism*
Substances
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Cell Cycle Proteins
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HSP70 Heat-Shock Proteins
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NPL4 protein, S cerevisiae
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Nucleocytoplasmic Transport Proteins
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SSZ1 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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UFD1 protein, S cerevisiae
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Vesicular Transport Proteins
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Proteasome Endopeptidase Complex
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Adenosine Triphosphatases
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CDC48 protein, S cerevisiae
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Valosin Containing Protein