SGD Paper 
Loscher M, et al. (2005) Interaction of U-box E3 ligase SNEV with PSMB4, the beta7 subunit of the 20 S proteasome. Biochem J 388(Pt 2):593-603
Abstract: Recognition of specific substrates for degradation by the ubiquitin/proteasome pathway is ensured by a cascade of ubiquitin transferases, E1, E2, and E3. The mechanism by which the target proteins are transported to the proteasome, is not clear, but two yeast E3s and one mammalian E3 ligase seem to be involved in delivery of targets to the proteasome, by escorting them and by binding to the 19S regulatory particle of the proteasome. Here we show that SNEV, a protein with in vitro E3 ligase activity, which is also involved in DNA repair and splicing, associates with the proteasome by directly binding to the beta7 subunit of the 20S proteasome. Upon inhibition of proteasome activity, SNEV does not accumulate within the cells although its colocalization with the proteasome increases significantly. Since immunofluorescence microscopy shows also increased colocalization of SNEV with ubiquitin after proteasome inhibition, without SNEV being ubiquitinated itself, we suggest that SNEV shows E3 ligase activity not only in vitro but also in vivo and escorts its substrate to the proteasome. Since the yeast homologue of SNEV, Prp19 also interacts with the yeast beta7 subunit of the proteasome, this mechanism seems to be conserved during evolution. Therefore, these data support the hypothesis, that E3 ligases might generally be involved in substrate transport to the proteasome. Additionally, our results provide the first evidence for a physical link between components of the ubiquitin/proteasome-system and the spliceosome.
| Status: Published | Type: Journal Article | PubMed ID: 15660529 |
Topics addressed in this paper
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