Protein misfolding is monitored by a variety of cellular "quality control" systems. Endoplasmic reticulum (ER) quality control handles misfolded secretory and membrane proteins and is well characterized. However, less is known about the quality control of misfolded cytosolic proteins (CytoQC). To study CytoQC, we have employed a genetic system in Saccharomyces cerevisiae using a transplantable degron, CL1 (1). Attachment of CL1 to the cytosolic protein Ura3p destabilizes Ura3p, targeting it for rapid proteasomal degradation. We have performed a comprehensive analysis of Ura3p-CL1 degradation requirements. As shown previously, we observe that the ER-localized ubiquitin E2 (Ubc6p, Ubc7p, and Cue1p) and E3 (Doa10p) machinery involved in ER-associated degradation (ERAD) are also responsible for the degradation of the cytosolic substrate Ura3p-CL1. Importantly, we find that the cytosol/ER membrane-localized chaperones Ydj1p and Ssa1p, known to be necessary for the ERAD of membrane proteins with misfolded cytosolic domains, are also required for the ubiquitination and degradation of Ura3p-CL1. In addition, we show a role for the Cdc48p-Npl4p-Ufd1p complex in the degradation of Ura3p-CL1. When ubiquitination is blocked, a portion of Ura3p-CL1 is ER membrane-localized. Furthermore, access to the cytosolic face of the ER is required for the degradation of CL1 degron-containing proteins. The ER is distributed throughout the cytosol, and our data, together with previous studies, suggest that the cytosolic face of the ER membrane serves as a "platform" for the degradation of Ura3p-CL1, which may also be the case for other CytoQC substrates.
Increase the total number of rows showing on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table.
| Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
|---|
Increase the total number of rows showing on this page using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i" buttons located within a cell for an annotation to view further details.
| Gene | Phenotype | Experiment Type | Mutant Information | Strain Background | Chemical | Details |
|---|---|---|---|---|---|---|
| CUE1 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | null Allele: cue1-Δ | Other | ||
| UBC6 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | null Allele: ubc6-Δ | Other | ||
| UBC7 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | null Allele: ubc7-Δ | Other | ||
| SSM4 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | null Allele: ssm4-Δ | Other | ||
| YDJ1 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | conditional Allele: ydj1-151 | Other | Temperature: elevated temperature, 37 °C | |
| NPL4 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | conditional Allele: npl4-1 G323S (nucleotide G967A) | Other | Temperature: elevated temperature, 37 °C | |
| CDC48 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | conditional Allele: cdc48-3 P257L, R387K; D1 ATPase domain mutated | Other | Temperature: elevated temperature, 37 °C | |
| UFD1 | protein/peptide accumulation: increased Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | conditional Allele: ufd1-1 V94D | Other | Temperature: elevated temperature, 37 °C | |
| SSM4 | protein/peptide modification: absent Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | null Allele: ssm4-Δ | Other | Details: ubiquination is absent | |
| YDJ1 | protein/peptide modification: absent Reporter: Ura3p-CL1 degron-containing version of URA3 | classical genetics | conditional Allele: ydj1-151 | Other | Temperature: elevated temperature, 37 °C Details: ubiquination is absent |