Reconstitution of an intact clock reveals mechanisms of circadian timekeeping

A biological clock in a test tube The biological clock of cyanobacteria, which remarkably requires just three proteins, has been reconstituted in vitro in a system that allows detailed study of its inputs and outputs, bringing new understanding of how environmental signals can influence a biological oscillator and how the clock controls cellular events such as gene transcription. Chavan et al . extended the known in vitro function of the core clock components to include output signals to transcriptional regulation and allow monitoring through fluorescence measurements in real time. The authors combined crystallography, mutagenesis, and quantitative modeling to further explore the clock mechanism, which may enable future synthetic biology applications. —LBR