The COP9 signalosome regulates the Neurospora circadian clock by controlling the stability of the SCFFWD-1 complex
The COP9 signalosome regulates the Neurospora circadian clock by controlling the stability of the SCFFWD-1 complex
复制标题
DOI：
10.1101/gad.1322205
复制
发表时间：
2005-07-01
影响因子：
10.5
通讯作者：
Liu, Y
中科院分区：
文献类型：
--
作者：
He, Q;Cheng, P;Liu, Y
COP9 信号体 (CSN) 在体内促进 SCF 型基于 cullin 的泛素连接酶复合物的功能。矛盾的是，CSN 去除 cullins 的 Nedd8 修饰会抑制体外 SCF 复合物的泛素连接酶活性。泛素化介导的脉孢菌昼夜节律时钟蛋白频率 (FRQ) 的降解对于时钟功能至关重要。 FRQ 的泛素化需要 FWD-1，即 SCF 复合物的底物招募亚基。在这里，我们发现 CSN (csn-2) 亚基的破坏会损害 FRQ 的降解并损害其正常的昼夜节律表达。不依赖于 FRQ 的振荡器驱动 csn-2 突变体中的分生孢子形成，从而产生在恒定黑暗 (DD)、恒定光照 (LL)、光到暗 (LD) 转变和温度循环中持续存在的二维分生孢子节律。引人注目的是，csn-2 突变体中 FWD-1 的水平急剧降低，这解释了 FRQ 降解受损的原因。突变体中 FWD-1 水平的降低需要其 F-box，表明其降解是由于自身泛素化所致。此外，SCFFWD-1复合物的SKP-1和CUL-1在突变体中也不稳定。因此，我们的结果证实了 CSN 在脉孢菌生物钟中的重要作用。我们的研究结果也调和了 CSN 悖论，并表明 CSN 的主要功能是维持体内 SCF 泛素连接酶的稳定性。
The COP9 signalosome (CSN) promotes the function of SCF-type cullin-based ubiquitin ligase complexes in vivo. Paradoxically, removal of the Nedd8 modification of cullins by CSN inhibits the ubiquitin ligase activity of SCF complexes in vitro. Ubiquitination-mediated degradation of the Neurospora circadian clock protein FREQUENCY (FRQ) is critical for clock function. Ubiquitination of FRQ requires FWD-1, the substrate-recruiting subunit of an SCF complex. Here we show that disruption of a subunit of CSN (csn-2) impairs the degradation of FRQ and compromises its normal circadian expression. A FRQ-independent oscillator drives conidiation in the csn-2 mutant, resulting in a 2-d conidiation rhythm that persists in constant darkness (DD), constant light (LL), light-to-dark (LD) transitions, and temperature cycles. Strikingly, the levels of FWD-1 are drastically reduced in csn-2 mutant, explaining the impaired degradation of FRQ. Reduction of FWD-1 levels in the mutant requires its F-box, suggesting that its degradation is due to autoubiquitination. In addition, SKP-1 and CUL-1 of the SCFFWD-1 complex are also unstable in the mutant. Therefore, our results establish an important role of CSN in the circadian clock of Neurospora. Our findings also reconcile the CSN paradox and suggest that a major function of CSN is to maintain the stability of SCF ubiquitin ligases in vivo.