Distinct ubiquitin ligases act sequentially for RNA polymerase II polyubiquitylation
Distinct ubiquitin ligases act sequentially for RNA polymerase II polyubiquitylation
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DOI：
10.1073/pnas.0907052106
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发表时间：
2009-12-08
影响因子：
11.1
通讯作者：
Svejstrup, Jesper Q.
中科院分区：
文献类型：
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作者：
Harreman, Michelle;Taschner, Michael;Svejstrup, Jesper Q.
蛋白酶体降解经过多聚泛素化修饰的蛋白质，因此正确控制泛素化对于避免必需蛋白质的意外蛋白水解至关重要。 RNAPII 蛋白水解的调节机制一直存在争议，因为两种不同的泛素连接酶 (E3)、Rsp5（及其人类同源物 NEDD4）和 Elongin-Cullin 复合物均已被证明是其 DNA 损伤诱导的多泛素化所必需的。在这里，我们展示了这些 E3 以两步机制顺序工作。首先，Rsp5 添加单泛素，或者有时添加通过泛素赖氨酸 63 连接的泛素链，不会触发蛋白水解。生成后，K63 链可被 Rsp5 相关泛素蛋白酶 Ubp2 修剪为单泛素化。基于 RNAPII 上的单泛素部分，Elc1/Cul3 复合物随后产生通过赖氨酸 48 连接的泛素链，这可以触发蛋白水解。同样，为了人类 RNAPII 的正确多泛素化，NEDD4 与 ElonginA/B/C-Cullin 5 复合物配合。这些数据表明，RNAPII 多泛素化需要不同的、顺序作用的泛素连接酶之间的合作，并提出了一个有趣的可能性，即 NEDD4 样泛素连接酶大且功能多样的家族的其他成员在靶向蛋白质降解时也需要第二个 E3 的帮助。
The proteasome degrades proteins modified by polyubiquitylation, so correctly controlled ubiquitylation is crucial to avoid unscheduled proteolysis of essential proteins. The mechanism regulating proteolysis of RNAPII has been controversial since two distinct ubiquitin ligases (E3s), Rsp5 (and its human homologue NEDD4) and Elongin-Cullin complex, have both been shown to be required for its DNA-damage-induced polyubiquitylation. Here we show that these E3s work sequentially in a two-step mechanism. First, Rsp5 adds mono-ubiquitin, or sometimes a ubiquitin chain linked via ubiquitin lysine 63 that does not trigger proteolysis. When produced, the K63 chain can be trimmed to mono-ubiquitylation by an Rsp5-associated ubiquitin protease, Ubp2. Based on this mono-ubiquitin moiety on RNAPII, an Elc1/Cul3 complex then produces a ubiquitin chain linked via lysine 48, which can trigger proteolysis. Likewise, for correct polyubiquitylation of human RNAPII, NEDD4 cooperates with the ElonginA/B/C-Cullin 5 complex. These data indicate that RNAPII polyubiquitylation requires cooperation between distinct, sequentially acting ubiquitin ligases, and raise the intriguing possibility that other members of the large and functionally diverse family of NEDD4-like ubiquitin ligases also require the assistance of a second E3 when targeting proteins for degradation.