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The N-end rule pathway is mediated by a complex of the RING-type Ubr1 and HECT-type Ufd4 ubiquitin ligases

Authors
Journal
Nature Cell Biology
1465-7392
Publisher
Nature Publishing Group
Publication Date
Volume
12
Issue
12
Identifiers
DOI: 10.1038/ncb2121
Keywords
  • Article
Disciplines
  • Biology

Abstract

Substrates of the N-end rule pathway are recognized by the Ubr1 E3 ubiquitin ligase through their destabilizing N-terminal residues. Our previous work showed that the Ubr1 E3 and the Ufd4 E3 co-target an internal degron of the Mgt1 DNA repair protein. Ufd4 is an E3 of the ubiquitin-fusion degradation (UFD) pathway that recognizes an N-terminal ubiquitin moiety. Here we report that the RING-type Ubr1 E3 and the HECT-type Ufd4 E3 interact, both physically and functionally. Although Ubr1 can recognize and polyubiquitylate an N-end rule substrate in the absence of Ufd4, the Ubr1-Ufd4 complex is more processive in that it produces a longer substrate-linked polyubiquitin chain. Conversely, Ubr1 can function as a polyubiquitylation-enhancing component of the Ubr1-Ufd4 complex in its targeting of UFD substrates. We also found that Ubr1 can recognize the N-terminal ubiquitin moiety. These and related advances unify two proteolytic systems that have been studied separately over two decades.

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