A genomic screen identifies Dsk2p and Rad23p as essential components of ER-associated degradation.
We developed a growth test to screen for yeast mutants defective in endoplasmic reticulum (ER) quality control and associated protein degradation (ERAD) using the membrane protein CTL*, a chimeric derivative of the classical ER degradation substrate CPY*. In a genomic screen of approximately 5,000 viable yeast deletion mutants, we identified genes necessary for ER quality control and degradation. Among the new gene products, we identified Dsk2p and Rad23p. We show that these two proteins are probably delivery factors for ubiquitinated ER substrates to the proteasome, following their removal from the membrane via the Cdc48-Ufd1-Npl4p complex. In contrast to the ERAD substrate CTG*, proteasomal degradation of a cytosolic CPY*-GFP fusion is not dependent on Dsk2p and Rad23p, indicating pathway specificity for both proteins. We propose that, in certain degradation pathways, Dsk2p, Rad23p and the trimeric Cdc48 complex function together in the delivery of ubiquitinated proteins to the proteasome, avoiding malfolded protein aggregates in the cytoplasm.
Medicherla
Balasubrahmanyam
B
Institut für Biochemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
Kostova
Zlatka
Z
Schaefer
Antje
A
Wolf
Dieter H
DH
D000251:Adenosine Triphosphatases; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D017353:Gene Deletion; D005821:Genetic Techniques; D016681:Genome, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D008956:Models, Chemical; D009154:Mutation; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D016366:Open Reading Frames; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017510:Protein Folding; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics* / Q000502:physiology*; D000074405:Valosin Containing Protein; D033921:Vesicular Transport Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C100415:DSK2 protein, S cerevisiae; C104361:NPL4 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; D011500:Protein Synthesis Inhibitors; C490846:RAD23 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C444652:UFD1 protein, S cerevisiae; D025801:Ubiquitin; D014452:Ubiquitins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; D003513:Cycloheximide; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein