An RNF11: Smurf2 complex mediates ubiquitination of the AMSH protein
An RNF11: Smurf2 complex mediates ubiquitination of the AMSH protein
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DOI：
10.1038/sj.onc.1207319
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发表时间：
2004-03-11
期刊：
影响因子：
8
通讯作者：
Seth, A
中科院分区：
文献类型：
--
作者：
Li, HX;Seth, A
环指蛋白在泛素化过程中起着重要作用，参与了多种细胞过程，包括信号转导、分化和凋亡。大多数环指蛋白具有E3-泛素连接酶活性。RNF 11是一种小环指蛋白，具有RING-H2结构域和PY基序，可以促进参与肿瘤发生的蛋白质：蛋白质相互作用。为了分离RNF 11蛋白伴侣并确定其在正常和癌细胞中的作用，我们进行了酵母双杂交筛选。在18个符合读码框的阳性克隆中，发现3个是ZBRK 1、Eps 15和AMSH（与STAM的SH 3结构域相关的分子）。ZBRK 1是一种含有KRAB结构域的锌指蛋白，已知其以BRCA 1依赖性方式抑制靶基因转录。Eps 15是monoubiquitinated的，是一个重要的复合物的一部分，通过网格蛋白介导的内化途径参与质膜受体的内吞作用。最近的研究表明AMSH蛋白通过与Smad 6和Smad 7结合参与BMP/TGF-β信号通路。RNF 11与这些结合伙伴的关联表明它将参与生物过程，如基因转录，BMP/TGF-β信号传导和泛素化相关事件。之前，我们已经证明RNF 11与HECT型E3连接酶AIP 4和Smurf 2相互作用。在这里，我们表明，RNF 11结合AMSH在哺乳动物细胞中，这种相互作用是独立的RNF 11环指结构域和PY基序。我们的研究结果还表明，AMSH是泛素化的Smurf 2 E3连接酶在RNF 11的存在下，其稳态水平随之减少需要RNF 11和Smurf 2。因此，RNF 11将AMSH招募到Smurf 2进行泛素化，导致其被26 S蛋白酶体降解。讨论了RNF 11介导的AMSH降解在乳腺癌中的潜在功能。
RING-finger proteins play crucial roles in ubiquitination events involved in diverse cellular processes including signal transduction, differentiation and apoptosis. Most of the RING-finger proteins have E3-ubiquitin ligase activity. RNF11 is a small RING-finger protein and harbors a RING-H2 domain and a PY motif that could facilitate protein: protein interaction(s) involved in oncogenesis. To isolate RNF11 protein partners and determine its role in normal and cancer cells, we performed yeast two-hybrid screening. Among 18 in-frame positive clones, three were found to be ZBRK1, Eps15 and AMSH ( associated molecule with the SH3 domain of STAM). ZBRK1 is a KRAB domain containing Zinc-finger protein and is known to repress target gene transcription in a BRCA1-dependent manner. Eps15 is monoubiquitinated and is part of an essential complex involved in the endocytosis of plasma membrane receptors via the clathrin-mediated internalization pathway. Recent studies have shown that AMSH protein is involved in BMP/TGF-beta signaling pathway by binding to Smad6 and Smad7. The association of RNF11 with these binding partners suggests that it would be involved in biological processes such as gene transcription, BMP/TGF-beta signaling and ubiquitination-associated events. Previously, we have shown that RNF11 interacts with the HECT-type E3 ligases AIP4 and Smurf2. Here, we show that RNF11 binds to AMSH in mammalian cells and that this interaction is independent of the RNF11 RING-finger domain and the PY motif. Our results also demonstrate that AMSH is ubiquitinated by Smurf2 E3 ligase in the presence of RNF11 and that a consequent reduction in its steady-state level requires both RNF11 and Smurf2. RNF11 therefore recruits AMSH to Smurf2 for ubiquitination, leading to its degradation by the 26S proteasome. The potential functions of RNF11-mediated degradation of AMSH in breast cancer are discussed.