Chuang SM and Madura K (2005) Saccharomyces cerevisiae Ub-conjugating enzyme Ubc4 binds the proteasome in the presence of translationally damaged proteins. Genetics 171(4):1477-84
Abstract: Surveillance mechanisms that monitor protein synthesis can promote rapid elimination of misfolded nascent proteins. We showed that the translation elongation factor eEF1A and the proteasome subunit Rpt1 play a central role in the translocation of nascent damaged proteins to the proteasome. We show here that multi-ubiquitinated proteins, and the ubiquitin-conjugating enzyme Ubc4, are rapidly detected in the proteasome following translational damage. However, Ubc4 levels in the proteasome were reduced significantly in a strain that expressed a mutant Rpt1 subunit. Ubc4 is an ideal candidate for ubiquitinating damaged nascent proteins, because it lacks significant substrate specificity, is required for the degradation of bulk, damaged proteins, and contributes to cellular stress-tolerance mechanisms. In agreement with this hypothesis, we determined that ubc4D ubc5D is exceedingly sensitive to protein translation inhibitors. Moreover, a nascently damaged test protein accumulated in proteasomes purified from ubc4D, suggesting a specific role for Ubc4/5 in the degradation of cotranslationally damaged proteins that are targeted to the proteasome.
|Status: Published||Type: Journal Article||PubMed ID: 16118187|
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