Non-transcriptional/translational regulations of the circadian system

Circadian clocks in organisms drive physiology and behavior, helping with adjustment to earths environment and human society. The generation and regulation mechanisms of circadian rhythms are starting to be understood. The transcriptional/post-transcriptional delayed feedback loop has been widely studied as the main regulation mechanism. But it cannot fully account for all circadian rhythms in cells. It has been reported that the "proto-clock" may have been a cytosolic metabolic oscillation and that the transcriptional translational regulation system, which provides robustness and amplifies circadian outputs, was developed during evolution. Research on circadian rhythms in cyanobacteria Synechococcus elongatus, algae Ostreococcus tauri, and human red blood cells in the absence of transcription and translation indicates the existence of a non-transcriptional/translational regulation mechanism, in addition to the classical transcriptional/translational regulation mechanism. It revealed a close link between the two regulation systems of circadian rhythms, in which they might complement each other. And NAD, involved in energy metabolism, may be involved in their interaction.