Setting a circadian clock: Structural understanding of the ligand-activation model of the circadian evening complex components ELF4 to ELF3

植物的生物钟驱动基因组规模的转录来协调大部分的生长和发育。早花3 （ELF3）是这种昼夜信号传导的关键枢纽。Davis小组最近表明，ELF3作为ELF4配体的受体整合体，一起被称为Evening Complex，启动这个基础上重要的抑制复合物。研究还表明，光抑制了这一作用，从而产生了一种假设，即光强度的增加加快了时钟的速度；光信号作为抑制因子的抑制因子。由于ELF3编码一种活性未知的蛋白质，它如何发挥关键的抑制作用仍然是个谜。在这里，我们提出了一个项目来解开一个时钟重置机制的ELF3。通过结合生化、细胞和结构实验，我们可以研究ELF3的时空功能。人们将监测这种染色质相关因子的全基因组结合，以确定其转录靶基因。接下来，我们将探索ELF4激活ELF3的定位背景，以及光感知如何抑制这一过程。将努力解决ELF4和ELF3的共复合体，并结合复合体组装的相关生物物理学，阐明ELF4结合如何改变ELF3折叠。由于已知ELF3被光感受器结合和抑制，因此将在可测试的背景下研究ELF4对ELF3的激活，以支持该关键时钟因子的“光感受器缓解”。总而言之，该项目旨在为时钟界长期存在的问题提供一个机制基础，该问题被称为夹带，其中光感知导致周期加速。这是对植物生物钟重置机制的首次描述。

The plant circadian clock drives genome-scale transcription to coordinate most of growth and development. EARLY FLOWERING 3 (ELF3) is the key hub for this diurnal signalling. The Davis group recently showed that ELF3 acts as a receptor integrator for the ELF4 ligand, together termed the Evening Complex, to initiate this foundationally important repressor complex. It was also shown that light represses this action, leading to a hypothesis for the mechanism by which increases in light intensity speed up the clock; light signalling acts as a repressor of a repressor. As ELF3 encodes a protein of unknown activity, it has remained enigmatic how it performs its key repressive role. Here we propose a project to unravel a clock-resetting mechanism by ELF3. Using a combination of biochemical, cellular and structural experiments, one would examine the spatial-temporal function of ELF3. One would monitor the global, genome-wide binding of this chromatin-associated factor to define its transcriptional target genes. Next an exploration of the localisation context of where ELF4 activates ELF3, and how light-perception represses this would be examined. Efforts to solve the co-complex of ELF4 and ELF3 will be undertaken and with associated biophysics of complex assembly, how ELF4 association alters ELF3 folding will be elucidated. As ELF3 is known to be bound and repressed by a photoreceptor, activation of ELF3 by ELF4 will be examined in a testable context that supports "photoreceptor-relief" of this key clock factor. Taken together this project is envisaged to provide one mechanistic basis of a long-standing problem in the clock community termed entrainment, where light perception leads to acceleration of periodicity. This is the first ever description of a clock-resetting mechanism in plants.