Chow Brenda Y, Sanchez Sabrina E, Breton Ghislain, Pruneda-Paz Jose L, Krogan Naden T, Kay Steve A
University of Southern California, Molecular and Computational Biology, Department of Biology Dana and David Dornsife College of Letters, Arts and Sciences, Los Angeles, CA 90089, USA.
Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
Curr Biol. 2014 Jul 7;24(13):1518-24. doi: 10.1016/j.cub.2014.05.029. Epub 2014 Jun 19.
Circadian clocks allow organisms to anticipate daily changes in the environment to enhance overall fitness. Transcription factors (TFs) play a prominent role in the molecular mechanism but are incompletely described possibly due to functional redundancy, gene family proliferation, and/or lack of context-specific assays. To overcome these, we performed a high-throughput yeast one-hybrid screen using the LUX ARRYHTHMO (LUX) gene promoter as bait against an Arabidopsis TF library. LUX is a unique gene because its mutation causes severe clock defects and transcript maintains high-amplitude cycling in the cold. We report the well-characterized cold-inducible C-repeat (CRT)/drought-responsive element (DRE) binding factor CBF1/DREB1b is a transcriptional regulator of LUX. We show that CBF1 binds the CRT in the LUX promoter, and both genes overlap in temporal and spatial expression. CBF1 overexpression causes upregulation of LUX and also alters other clock gene transcripts. LUX promoter regions including the CRT and Evening Element (EE) are sufficient for high-amplitude transcriptional cycling in the cold, and cold-acclimated lux seedlings are sensitive to freezing stress. Our data show cold signaling is integrated into the clock by CBF-mediated regulation of LUX expression, thereby defining a new transcriptional mechanism for temperature input to the circadian clock.
生物钟使生物体能够预测环境中的每日变化，以提高整体适应性。转录因子（TFs）在分子机制中起着重要作用，但由于功能冗余、基因家族增殖和/或缺乏特定背景的检测方法，其作用尚未得到充分描述。为了克服这些问题，我们以拟南芥转录因子文库为对象，以LUX ARRYHTHMO（LUX）基因启动子为诱饵，进行了高通量酵母单杂交筛选。LUX是一个独特的基因，因为它的突变会导致严重的生物钟缺陷，并且其转录本在低温下保持高振幅循环。我们报告了特征明确的冷诱导C-重复序列（CRT）/干旱响应元件（DRE）结合因子CBF1/DREB1b是LUX的转录调节因子。我们发现CBF1与LUX启动子中的CRT结合，并且这两个基因在时空表达上重叠。CBF1的过表达导致LUX上调，同时也改变了其他生物钟基因的转录本。包括CRT和晚间元件（EE）的LUX启动子区域足以在低温下进行高振幅转录循环，并且冷驯化的lux幼苗对冷冻胁迫敏感。我们的数据表明，冷信号通过CBF介导的LUX表达调控被整合到生物钟中，从而定义了一种新的温度输入到生物钟的转录机制。
