Reinke Hans, Saini Camille, Fleury-Olela Fabienne, Dibner Charna, Benjamin Ivor J, Schibler Ueli
Department of Molecular Biology, University of Geneva, CH-1211 Geneva, Switzerland.
Genes Dev. 2008 Feb 1;22(3):331-45. doi: 10.1101/gad.453808.
The circadian clock enables the anticipation of daily recurring environmental changes by presetting an organism's physiology and behavior. Driven and synchronized by a central pacemaker in the brain, circadian output genes fine-tune a wide variety of physiological parameters in peripheral organs. However, only a subset of circadianly transcribed genes seems to be directly regulated by core clock proteins. Assuming that yet unidentified transcription factors may exist in the circadian transcriptional network, we set out to develop a novel technique, differential display of DNA-binding proteins (DDDP), which we used to screen mouse liver nuclear extracts. In addition to several established circadian transcription factors, we found DNA binding of heat-shock factor 1 (HSF1) to be highly rhythmic. HSF1 drives the expression of heat-shock proteins at the onset of the dark phase, when the animals start to be behaviorally active. Furthermore, Hsf1-deficient mice have a longer free-running period than wild-type littermates, suggesting a combined role for HSF1 in the mammalian timekeeping and cytoprotection systems. Our results also suggest that the new screening method DDDP is not limited to the identification of circadian transcription factors but can be applied to discover novel transcriptional regulators in various biological systems.
生物钟通过预设生物体的生理和行为，使其能够预测每日反复出现的环境变化。在大脑中央起搏器的驱动和同步作用下，生物钟输出基因对外周器官中的各种生理参数进行微调。然而，似乎只有一部分生物钟转录基因直接受核心生物钟蛋白调控。假设生物钟转录网络中可能存在尚未鉴定的转录因子，我们着手开发一种新技术——DNA结合蛋白差异显示（DDDP），并用于筛选小鼠肝细胞核提取物。除了几种已确定的生物钟转录因子外，我们发现热休克因子1（HSF1）的DNA结合具有高度节律性。在黑暗期开始时，当动物开始活跃时，HSF1驱动热休克蛋白的表达。此外，Hsf1基因缺陷小鼠的自由活动周期比野生型同窝小鼠长，这表明HSF1在哺乳动物计时和细胞保护系统中具有联合作用。我们的结果还表明，新的筛选方法DDDP不仅限于鉴定生物钟转录因子，还可应用于发现各种生物系统中的新型转录调节因子。
