Modification of yeast Cdc53p by the ubiquitin-related protein Rub1p affects function of the SCFCdc4 complex (original) (raw)
- Doug Lammer,
- Neal Mathias,
- Jose M. Laplaza,
- Weidong Jiang,
- Yun Liu,
- Judy Callis,
- Mark Goebl, and
- Mark Estelle
- Biology Department, Indiana University, Bloomington, Indiana, 47405 USA; Biochemistry and Molecular Biology Department and the Walther Oncology Center, Indiana University Medical School, Indianapolis, Indiana 46202 USA; Section of Molecular and Cellular Biology, University of California–Davis, Davis, California 95616 USA; Microcide Pharmaceuticals Inc., Mountain View, California 94043 USA
Abstract
The RUB1/NEDD-8 family of ubiquitin-related genes is widely represented among eukaryotes. Here we report that Cdc53p in Saccharomyces cerevisiae, a member of the Cullin family of proteins, is stably modified by the covalent attachment of a single Rub1p molecule. Two genes have been identified that are required for Rub1p conjugation to Cdc53p. The first gene, designated_ENR2,_ encodes a protein with sequence similarity to the amino-terminal half of the ubiquitin-activating enzyme. By analogy with Aos1p, we infer that Enr2p functions in a bipartite Rub1p-activating enzyme. The second gene is SKP1, shown previously to be required for some ubiquitin–conjugation events. A deletion allele of_ENR2_ is lethal with temperature-sensitive alleles of_cdc34_ and enhances the phenotypes of cdc4, cdc53, and_skp1,_ strongly implying that Rub1p conjugation to Cdc53p is required for optimal assembly or function of the E3 complex SCFCdc4. Consistent with this model, both_enr2Δ_ and an allele of Cdc53p that is not Rub1p modified, render cells sensitive to alterations in the levels of Cdc4p, Cdc34p, and Cdc53p.
