Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT, 06511, USA.
Nat Commun. 2019 Aug 21;10(1):3750. doi: 10.1038/s41467-019-11769-7.
ZEITLUPE (ZTL), a photoreceptor with E3 ubiquitin ligase activity, communicates end-of-day light conditions to the plant circadian clock. It still remains unclear how ZTL protein accumulates in the light but does not destabilize target proteins before dusk. Two deubiquitylating enzymes, UBIQUITIN-SPECIFIC PROTEASE 12 and 13 (UBP12 and UBP13), which regulate clock period and protein ubiquitylation in a manner opposite to ZTL, associate with the ZTL protein complex. Here we demonstrate that the ZTL interacting partner, GIGANTEA (GI), recruits UBP12 and UBP13 to the ZTL photoreceptor complex. We show that loss of UBP12 and UBP13 reduces ZTL and GI protein levels through a post-transcriptional mechanism. Furthermore, a ZTL target protein is unable to accumulate to normal levels in ubp mutants. This demonstrates that the ZTL photoreceptor complex contains both ubiquitin-conjugating and -deconjugating enzymes, and that these two opposing enzyme types are necessary for circadian clock pacing. This shows that deubiquitylating enzymes are a core element of circadian clocks, conserved from plants to animals.
ZEITLUPE（ZTL）是一种具有 E3 泛素连接酶活性的光受体，它将一天结束时的光照条件传递给植物生物钟。目前仍不清楚为什么 ZTL 蛋白在光照下积累，但在黄昏前不会使靶蛋白不稳定。两种去泛素化酶，即泛素特异性蛋白酶 12 和 13（UBP12 和 UBP13），以与 ZTL 相反的方式调节生物钟周期和蛋白质泛素化，与 ZTL 蛋白复合物相关联。在这里，我们证明 ZTL 的相互作用伙伴 GI 招募 UBP12 和 UBP13 到 ZTL 光受体复合物。我们表明，UBP12 和 UBP13 的缺失通过转录后机制降低了 ZTL 和 GI 蛋白水平。此外，UBP 突变体中 ZTL 靶蛋白无法正常积累。这表明 ZTL 光受体复合物既包含泛素连接酶又包含去泛素化酶，并且这两种相反的酶类型对于生物钟起搏是必需的。这表明去泛素化酶是从植物到动物的生物钟的核心组成部分。
