Consortium CSIC-IRTA-UAB, Centre for Research in Agricultural Genomics, Department of Plant Molecular Genetics, Barcelona, Spain.
PLoS Genet. 2010 Nov 4;6(11):e1001201. doi: 10.1371/journal.pgen.1001201.
Circadian rhythms are daily biological oscillations driven by an endogenous mechanism known as circadian clock. The protein kinase CK2 is one of the few clock components that is evolutionary conserved among different taxonomic groups. CK2 regulates the stability and nuclear localization of essential clock proteins in mammals, fungi, and insects. Two CK2 regulatory subunits, CKB3 and CKB4, have been also linked with the Arabidopsis thaliana circadian system. However, the biological relevance and the precise mechanisms of CK2 function within the plant clockwork are not known. By using ChIP and Double-ChIP experiments together with in vivo luminescence assays at different temperatures, we were able to identify a temperature-dependent function for CK2 modulating circadian period length. Our study uncovers a previously unpredicted mechanism for CK2 antagonizing the key clock regulator CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1). CK2 activity does not alter protein accumulation or subcellular localization but interferes with CCA1 binding affinity to the promoters of the oscillator genes. High temperatures enhance the CCA1 binding activity, which is precisely counterbalanced by the CK2 opposing function. Altering this balance by over-expression, mutation, or pharmacological inhibition affects the temperature compensation profile, providing a mechanism by which plants regulate circadian period at changing temperatures. Therefore, our study establishes a new model demonstrating that two opposing and temperature-dependent activities (CCA1-CK2) are essential for clock temperature compensation in Arabidopsis.
昼夜节律是由一种称为生物钟的内源性机制驱动的每日生物振荡。蛋白激酶 CK2 是少数在不同分类群中进化保守的时钟成分之一。CK2 调节哺乳动物、真菌和昆虫中必需时钟蛋白的稳定性和核定位。两种 CK2 调节亚基 CKB3 和 CKB4 也与拟南芥生物钟系统有关。然而，CK2 在植物生物钟中的生物学相关性和精确作用机制尚不清楚。通过使用 ChIP 和 Double-ChIP 实验以及在不同温度下进行体内发光测定，我们能够鉴定出 CK2 调节昼夜节律周期长度的温度依赖性功能。我们的研究揭示了 CK2 拮抗关键生物钟调节剂 CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) 的一个以前未预测的机制。CK2 活性不会改变蛋白质积累或亚细胞定位，但会干扰 CCA1 与振荡器基因启动子的结合亲和力。高温增强了 CCA1 的结合活性，而 CK2 的拮抗功能则精确地平衡了这种活性。通过过表达、突变或药理学抑制改变这种平衡会影响温度补偿谱，为植物在不同温度下调节生物钟周期提供了一种机制。因此，我们的研究建立了一个新的模型，表明两种相反且依赖于温度的活性（CCA1-CK2）对于拟南芥生物钟的温度补偿是必不可少的。
