Kohlmann S~Wolf DH, 2008

Pubmed ID 18436532
Title Ubiquitin ligase Hul5 is required for fragment-specific substrate degradation in endoplasmic reticulum-associated degradation.
Authors Sonja Kohlmann, Antje Schäfer, Dieter H Wolf
Abstract To identify new components of the protein quality control and degradation pathway of the endoplasmic reticulum (ER), we performed a growth-based genome-wide screen of about 5000 viable deletion mutants of the yeast Saccharomyces cerevisiae. As substrates we used two misfolded ER membrane proteins, CTL* and Sec61-2L, chimeric derivatives of the classical ER degradation substrates CPY* and Sec61-2. Both substrates contain a cytosolic Leu2 protein fusion, and stabilization of these substrates in ER-associated degradation-deficient strains enables a restored growth of the transformed LEU2-deficient deletion mutants. We identified the strain deleted for the ubiquitin chain elongating ligase Hul5 among the mutant strains with a strong growth phenotype. Here we show that Hul5 is necessary for the degradation of two misfolded ER membrane substrates. Although the degradation of their N-terminal parts is Hul5-independent, the breakdown of their C-terminal fragments requires the ubiquitin chain elongating ligase activity of Hul5. In the absence of Hul5, a truncated form of CTL*myc remains to a large extent embedded in the ER membrane. Hul5 activity promotes the interaction of this truncated CTL*myc with the AAA-ATPase Cdc48, which is known to pull proteins out of the ER membrane. This study unravels the stepwise elimination of the ER membrane-localized CTL*myc substrate. First, N-terminal, lumenal CPY* is transferred to the cytoplasm and degraded by the proteasome. Subsequently, the remaining C-terminal membrane-anchored part requires Hul5 for its effective extraction out of the endoplasmic reticulum and proteasomal degradation.
Citation J. Biol. Chem. 2008; 283:16374-83


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Papers Phenotype Conditions Collection Tested mutants Data Details
Kohlmann S~Wolf DH, 2008 ER-associated protein degradation hom ~5,000 None

Curation history


June 27, 2016 Data requested.
June 23, 2016 Data to request.
Aug. 16, 2016 Data abandoned.

Tested strains

June 23, 2016 Tested strains to request.
June 27, 2016 Tested strains requested.
Aug. 16, 2016 Tested strains abandoned.