The TRC8 ubiquitin ligase is sterol regulated and interacts with lipid and protein biosynthetic pathways.
The TRC8 ubiquitin ligase is sterol regulated and interacts with lipid and protein biosynthetic pathways.
复制标题
DOI：
10.1158/1541-7786.mcr-08-0491
复制
发表时间：
2010-01
期刊：
影响因子：
--
通讯作者：
Gemmill RM
中科院分区：
文献类型：
--
作者：
Lee JP;Brauweiler A;Rudolph M;Hooper JE;Drabkin HA;Gemmill RM
TRC 8/RNF 139编码ER-驻留E3-泛素连接酶，其以RING和泛素化依赖性方式抑制生长。TRC 8还含有预测的固醇敏感结构域。在这里，我们报告说，TRC 8蛋白水平是甾醇响应，它结合并刺激ER锚定蛋白，INSIG的泛素化。TRC 8的诱导使转录因子SREBP-1和SREBP-2的前体形式不稳定。SREBP前体的丢失是蛋白酶体依赖性的，需要一个功能性的RING结构域，发生时不产生加工的核形式和抑制SREBP靶基因。TRC 8敲低在固醇剥夺的细胞中具有相反的效果。在果蝇中，DTrc 8对生长的抑制作用在遗传上受到COP 9信号体和eIF 3中含有特定MPN结构域的蛋白质的抑制。DTrc 8与eIF 3的两个亚基eIF 3f和eIF 3 h相互作用。免疫共沉淀实验证实了哺乳动物细胞中的这些相互作用和TRC 8过表达抑制多核糖体谱。此外，高分子量泛素化蛋白质中观察到eIF 3免疫沉淀从TRC 8过表达细胞。因此，TRC 8功能可以提供脂质和蛋白质生物合成途径之间的调节联系。
TRC8/RNF139 encodes an ER-resident E3-ubiquitin ligase that inhibits growth in a RING- and ubiquitylation-dependent manner. TRC8 also contains a predicted sterol-sensing domain. Here we report that TRC8 protein levels are sterol-responsive, and that it binds and stimulates ubiquitylation of the ER-anchor protein, INSIG. Induction of TRC8 destabilized the precursor forms of the transcription factors, SREBP-1 and SREBP-2. Loss of SREBP precursors was proteasome-dependent, required a functional RING domain, occurred without generating processed nuclear forms and suppressed SREBP target genes. TRC8 knockdown had opposite effects in sterol-deprived cells. In Drosophila, growth inhibition by DTrc8 was genetically suppressed by loss of specific MPN domain-containing proteins found in the COP9 signalosome and eIF3. DTrc8 genetically and physicially interacted with two eIF3 subunits, eIF3f and eIF3h. Co-immunoprecipitation experiments confirmed these interactions in mammalian cells and TRC8 over-expression suppressed polysome profiles. Moreover, high molecular weight ubiquitylated proteins were observed in eIF3 immunoprecipitations from TRC8 over-expressing cells. Thus, TRC8 function may provide a regulatory link between the lipid and protein biosynthetic pathways.