UBXN7 docks on neddylated cullin complexes using its UIM motif and causes HIF1α accumulation.
UBXN7 docks on neddylated cullin complexes using its UIM motif and causes HIF1α accumulation.
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DOI：
10.1186/1741-7007-10-36
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发表时间：
2012-04-26
期刊：
影响因子：
5.4
通讯作者：
Alexandru G
中科院分区：
文献类型：
--
作者：
Bandau S;Knebel A;Gage ZO;Wood NT;Alexandru G
Uba-Ubx家族的蛋白通过其Uba结构域与泛素化蛋白相互作用，并通过其Ubx结构域与p97相互作用，从而充当p97 ATPase的底物结合接头。特别是，人UBXN7(也称为UBXD7)介导p97与转录因子HIF1α的相互作用，该转录因子在正常氧细胞中通过基于CUL2的E3连接酶CRL2活跃地泛素化。Uba-Ubx蛋白免疫沉淀物的质谱分析表明，它们与大量的E3泛素连接酶相互作用。值得注意的是，UBXN7最擅长与剔除环连合酶亚基相互作用。因此，我们开始确定UBXN7与Cullins的相互作用是直接的，还是由其与UBA结构域结合的泛素化靶标介导的。我们证明UBXN7与库林斯的相互作用不依赖于泛素和底物的结合。相反，它依赖于UBXN7中的UIM基序，该基序直接参与对Cullins的NEDD8修改。为了了解UBXN7与neddylated cullins相互作用的功能后果，我们重点研究了HIF1CUL2底物，它使用UBXD7/p97作为泛素受体，在蛋白酶体介导的降解过程中。我们发现，UBXN7的过表达将CUL2转化为其非泛素化形式，并导致非泛素化的HIF1α的积累。这两种效应都是严格依赖于UIM的，只有当UBXN7包含完整的UIM基序时才会发生。我们还表明，携带较长泛素链的HIF1α可以招募替代泛素受体，但缺乏p97‘S依赖的分离酶活性。我们的研究表明，UBXN7独立于其作为p97泛素结合接头的功能，直接与缺陷型库林斯相互作用，并导致CUL2底物HIF1α的积聚。我们认为，UBXN7通过隔离CUL2的缺失形式，负性调节CRL2的泛素连接酶活性，这可能阻止p97以外的泛素受体重新募集到核HIF1α。
The proteins from the UBA-UBX family interact with ubiquitylated proteins via their UBA domain and with p97 via their UBX domain, thereby acting as substrate-binding adaptors for the p97 ATPase. In particular, human UBXN7 (also known as UBXD7) mediates p97 interaction with the transcription factor HIF1α that is actively ubiquitylated in normoxic cells by a CUL2-based E3 ligase, CRL2. Mass spectrometry analysis of UBA-UBX protein immunoprecipitates showed that they interact with a multitude of E3 ubiquitin-ligases. Conspicuously, UBXN7 was most proficient in interacting with cullin-RING ligase subunits. We therefore set out to determine whether UBXN7 interaction with cullins was direct or mediated by its ubiquitylated targets bound to the UBA domain. We show that UBXN7 interaction with cullins is independent of ubiquitin- and substrate-binding. Instead, it relies on the UIM motif in UBXN7 that directly engages the NEDD8 modification on cullins. To understand the functional consequences of UBXN7 interaction with neddylated cullins, we focused on HIF1α, a CUL2 substrate that uses UBXD7/p97 as a ubiquitin-receptor on its way to proteasome-mediated degradation. We find that UBXN7 over-expression converts CUL2 to its neddylated form and causes the accumulation of non-ubiquitylated HIF1α. Both of these effects are strictly UIM-dependent and occur only when UBXN7 contains an intact UIM motif. We also show that HIF1α carrying long ubiquitin-chains can recruit alternative ubiquitin-receptors, lacking p97's ATP-dependent segregase activity. Our study shows that independently of its function as a ubiquitin-binding adaptor for p97, UBXN7 directly interacts with neddylated cullins and causes the accumulation of the CUL2 substrate HIF1α. We propose that by sequestering CUL2 in its neddylated form, UBXN7 negatively regulates the ubiquitin-ligase activity of CRL2 and this might prevent recruitment of ubiquitin-receptors other than p97 to nuclear HIF1α.
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影响因子：
64.5
作者：
Duda, David M.;Borg, Laura A.;Scott, Daniel C.;Hunt, Harold W.;Hammel, Michal;Schulman, Brenda A.
通讯作者：
Schulman, Brenda A.
影响因子：
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影响因子：
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影响因子：
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