Post-translational regulation of the Arabidopsis circadian clock through selective proteolysis and phosphorylation of pseudo-response regulator proteins
Post-translational regulation of the Arabidopsis circadian clock through selective proteolysis and phosphorylation of pseudo-response regulator proteins
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DOI：
10.1074/jbc.m803471200
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发表时间：
2008-08-22
影响因子：
4.8
通讯作者：
Somers, David E.
中科院分区：
文献类型：
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作者：
Fujiwara, Sumire;Wang, Lei;Somers, David E.
昼夜节律钟控制着周期、相位和振幅，以接近24小时的节奏振荡。拟南芥中控制中央振荡器速度的一个核心时钟组件组由5个伪反应调节蛋白（PRR）组成，其在时钟中的生化功能尚不清楚。TOC1 (cab表达时间1)/PRR1、PRR3、PRR5、PRR7和PRR9的峰值表达在一天中各有不同的阶段，任何PRR蛋白的缺失都会改变周期。我们发现，除了TOC1外，PRR5是该PRR家族中E3泛素连接酶SCFZTL唯一可能的蛋白水解底物。我们进一步证明了PRR5、TOC1和PRR3磷酸化形式的功能意义。所检测的每一种PRR蛋白都是核定位的，并且在昼夜周期中被不同的磷酸化。PRR5和TOC1的高度磷酸化形式与F-box蛋白ZTL （ZEITLUPE）相互作用最好，这表明一种调节它们蛋白水解的机制。在体内PRR5和ZTL的降解都受到蓝光的抑制，这可能是ZTL对蓝光光感知的结果。TOC1和PRR3在体内相互作用，两者的磷酸化是它们在体外最佳结合的必要条件。此外，由于PRR3和ZTL在体内都通过TOC1 N端与TOC1相互作用，综合这些数据表明，TOC1/PRR3磷酸化依赖的相互作用可能保护TOC1免受ZTL介导的降解，导致TOC1循环的振幅增强。
The circadian clock controls the period, phasing, and amplitude of processes that oscillate with a near 24-h rhythm. One core group of clock components in Arabidopsis that controls the pace of the central oscillator is comprised of five PRR (pseudo-response regulator) proteins whose biochemical function in the clock remains unclear. Peak expression of TOC1 (timing of cab expression 1)/PRR1, PRR3, PRR5, PRR7, and PRR9 are each phased differently over the course of the day and loss of any PRR protein alters period. Here we show that, together with TOC1, PRR5 is the only other likely proteolytic substrate of the E3 ubiquitin ligase SCFZTL within this PRR family. We further demonstrate a functional significance for the phosphorylated forms of PRR5, TOC1, and PRR3. Each PRR protein examined is nuclear-localized and is differentially phosphorylated over the circadian cycle. The more highly phosphorylated forms of PRR5 and TOC1 interact best with the F-box protein ZTL (ZEITLUPE), suggesting a mechanism to modulate their proteolysis. In vivo degradation of both PRR5 and ZTL is inhibited by blue light, likely the result of blue light photoperception by ZTL. TOC1 and PRR3 interact in vivo and phosphorylation of both is necessary for their optimal binding in vitro. Additionally, because PRR3 and ZTL both interact with TOC1 in vivo via the TOC1 N terminus, taken together these data suggest that the TOC1/PRR3 phosphorylation-dependent interaction may protect TOC1 from ZTL-mediated degradation, resulting in an enhanced amplitude of TOC1 cycling.