A broad category of proteins that regulate the CIRCADIAN RHYTHM of an organism. Included here are proteins that transmit intracellular and intercellular signals in a chronological manner along with proteins that sense light and time-dependent changes in the environment such as the PHOTOPERIOD.

Synonyms: Circadian Rhythm Signaling Peptides and Proteins, 0, Circadian Clock Proteins and Peptides, Circadian Rhythm Signaling Peptides, Circadian Rhythm Signaling Proteins