Molecular components of the Mammalian circadian clock

TLDR: This work has shown that there are other molecular circadian oscillators which can act independently of the transcription-based clock in all species which have been tested.

Abstract: Mammals synchronize their circadian activity primarily to the cycles of light and darkness in the environment This is achieved by ocular photoreception relaying signals to the suprachiasmatic nucleus (SCN) in the hypothalamus Signals from the SCN cause the synchronization of independent circadian clocks throughout the body to appropriate phases Signals that can entrain these peripheral clocks include humoral signals, metabolic factors, and body temperature At the level of individual tissues, thousands of genes are brought to unique phases through the actions of a local transcription/translation-based feedback oscillator and systemic cues In this molecular clock, the proteins CLOCK and BMAL1 cause the transcription of genes which ultimately feedback and inhibit CLOCK and BMAL1 transcriptional activity Finally, there are also other molecular circadian oscillators which can act independently of the transcription-based clock in all species which have been tested