Regulation of Tsg101 expression by the steadiness box: A role of Tsg101-associated ligase
Regulation of Tsg101 expression by the steadiness box: A role of Tsg101-associated ligase
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DOI：
10.1091/mbc.e07-09-0957
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发表时间：
2008-02-01
影响因子：
3.3
通讯作者：
Martin-Serrano, Juan
中科院分区：
文献类型：
--
作者：
McDonald, Bethan;Martin-Serrano, Juan
作为运输所需的内体分选复合体(ESCRT)机械的一部分，Tsg101在内体分选、膜受体降解和细胞质分裂的最后阶段是必不可少的。蛋白质的耗尽或过度生产会导致这些重要过程的中断，并对细胞造成严重后果。因此，Tsg101的表达在翻译后被控制在一个很小的范围内，这种自我调节已经被映射到蛋白质的C末端。在这里，我们进一步阐明了这种调控的机制，并描述了Tsg101相关连接酶(Tal)在介导这种调控中的一个新功能。我们发现Tal多泛素化未复合的Tsg101的C-末端的赖氨酸残基，导致蛋白酶体的降解。然而，这些赖氨酸的可及性被其他ESCRT-I蛋白的存在所阻止。我们发现VPS28是一个限制因子，因此ESCRT-I功能过剩的Tsg101表达很容易被降解。当Tsg101过表达时，Tal在Tsg101稳态调控中的作用被突显出来；然而，我们的数据也表明，在正常条件下，额外的连接酶调节Tsg101的表达。最后，我们证明，虽然C-末端赖氨酸是多泛素化的靶标，但它们不是ESCRT活性所必需的任何额外功能所必需的。
As part of the endosomal sorting complex required for transport (ESCRT) machinery, Tsg101 is essential for endosomal sorting, membrane receptor degradation and the final stages of cytokinesis. Depletion or overproduction of the protein can cause disruption of these vital processes and results in severe consequences for the cell. Tsg101 expression is thus controlled posttranslationally within a narrow range and this autoregulation has been mapped to the C-terminus of the protein. Here we elucidate further the mechanisms of this regulation and describe a novel function of Tsg101-associated ligase ( Tal) in mediating this control. We show that Tal polyubiquitinates lysine residues in the C-terminus of uncomplexed Tsg101, resulting in proteasomal degradation. However, accessibility to these lysines is prevented by the presence of the other ESCRT-I proteins. We show that VPS28 is a limiting factor, and consequently Tsg101 expression surplus to ESCRT-I function is vulnerable to degradation. The role of Tal in the regulation of Tsg101 steady-state control is highlighted when Tsg101 is overexpressed; however, our data also suggest that additional ligases regulate Tsg101 expression under normal conditions. Lastly, we demonstrate that while the C-terminal lysines are targets for polyubiquitination, they are not required for any additional function necessary for ESCRT activity.