A novel protein modification pathway related to the ubiquitin system

Ubiquitin conjugation is known to target protein substrates primarily to degradation by the proteasome or via the endocytic route. Here we describe a novel protein modification pathway in yeast which mediates the conjugation of RUB1, a ubiquitin‐like protein displaying 53% amino acid identity to ubi...

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Bibliographic Details
Published in:The EMBO journal 1998-04, Vol.17 (8), p.2208-2214
Main Authors: Liakopoulos, Dimitris, Doenges, Georg, Matuschewski, Kai, Jentsch, Stefan
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Base Sequence
CDC53
Cell Cycle Proteins - metabolism
cullin
Cullin Proteins
DNA, Complementary
Fungal Proteins - genetics
Fungal Proteins - metabolism
Ligases - metabolism
Molecular Sequence Data
NEDD8
RUB1
Saccharomyces cerevisiae
Saccharomyces cerevisiae Proteins
Sequence Homology, Amino Acid
Substrate Specificity
ubiquitin
Ubiquitin-Activating Enzymes
Ubiquitin-Conjugating Enzymes
Ubiquitin-Protein Ligases
Ubiquitins - metabolism
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Summary:Ubiquitin conjugation is known to target protein substrates primarily to degradation by the proteasome or via the endocytic route. Here we describe a novel protein modification pathway in yeast which mediates the conjugation of RUB1, a ubiquitin‐like protein displaying 53% amino acid identity to ubiquitin. We show that RUB1 conjugation requires at least three proteins in vivo. ULA1 and UBA3 are related to the N‐ and C‐terminal domains of the E1 ubiquitin‐activating enzyme, respectively, and together fulfil E1‐like functions for RUB1 activation. RUB1 conjugation also requires UBC12, a protein related to E2 ubiquitin‐conjugating enzymes, which functions analogously to E2 enzymes in RUB1–protein conjugate formation. Conjugation of RUB1 is not essential for normal cell growth and appears to be selective for a small set of substrates. Remarkably, CDC53/cullin, a common subunit of the multifunctional SCF ubiquitin ligase, was found to be a major substrate for RUB1 conjugation. This suggests that the RUB1 conjugation pathway is functionally affiliated to the ubiquitin–proteasome system and may play a regulatory role.
ISSN:0261-4189
1460-2075
1460-2075
DOI:10.1093/emboj/17.8.2208