Interaction of U-box E3 ligase SNEV with PSMB4, the β7 subunit of the 20 S proteasome
Interaction of U-box E3 ligase SNEV with PSMB4, the β7 subunit of the 20 S proteasome
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DOI：
10.1042/bj20041517
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发表时间：
2005-06-01
影响因子：
4.1
通讯作者：
Grillari, J
中科院分区：
文献类型：
--
作者：
Löscher, M;Fortschegger, K;Grillari, J
通过泛素-蛋白酶体途径降解的特异性底物的识别由泛素转移酶E1、E2和E3的级联确保。靶蛋白被转运到蛋白酶体的机制尚不清楚，但两个酵母E3和一个哺乳动物E3连接酶似乎参与了靶蛋白到蛋白酶体的递送，通过护送它们和通过结合到蛋白酶体的19 S调节颗粒。在本研究中，我们发现SNEV（衰老逃避因子），一种具有体外E3连接酶活性的蛋白质，也参与DNA修复和剪接，通过直接结合20 S蛋白酶体的β 7亚基与蛋白酶体相关联。在蛋白酶体活性抑制后，SNEV不会在细胞内积累，尽管其与蛋白酶体的共定位显著增加。由于免疫荧光显微镜也显示蛋白酶体抑制后，增加了与泛素的SNEV的共定位，而SNEV本身没有被泛素化，我们认为SNEV不仅在体外，而且在体内显示E3连接酶活性，并护送其底物的蛋白酶体。由于SNEV的酵母同源物Prp 19也与蛋白酶体的酵母β 7亚基相互作用，因此这种机制似乎在进化过程中是保守的。因此，这些结果支持的假设，E3连接酶可能通常参与底物运输到蛋白酶体。此外，我们的研究结果提供了第一个证据，泛素-蛋白酶体系统和剪接体的组件之间的物理联系。
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 the delivery of targets to the proteasome, by escorting them and by binding to the 19 S regulatory particle of the proteasome. In the present study, we show that SNEV (senescence evasion factor), 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 beta 7 subunit of the 20 S proteasome. Upon inhibition of proteasome activity, SNEV does not accumulate within the cells although its co-localization with the proteasome increases significantly. Since immunofluorescence microscopy also shows increased co-localization of SNEV with ubiquitin after proteasome inhibition, without SNEV being ubiquitinated by 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, Prp 19, also interacts with the yeast beta 7 subunit of the proteasome, this mechanism seems to be conserved during evolution. Therefore these results 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.