The protein encoded by this gene plays a central role in the regulation of circadian rhythms. The protein encodes a transcription factor of the basic helix-loop-helix (bHLH) family and contains DNA binding histone acetyltransferase activity. The encoded protein forms a heterodimer with ARNTL (BMAL1) that binds E-box enhancer elements upstream of Period (PER1, PER2, PER3) and Cryptochrome (CRY1, CRY2) genes and activates transcription of these genes. PER and CRY proteins heterodimerize and repress their own transcription by interacting in a feedback loop with CLOCK/ARNTL complexes. Polymorphisms in this gene may be associated with behavioral changes in certain populations and with obesity and metabolic syndrome. Alternative splicing results in multiple transcript variants.CLOCK (Clock Circadian Regulator) is a Protein Coding gene. Diseases associated with CLOCK include Delayed Sleep Phase Syndrome and Cluster Headache. Among its related pathways are Circadian rythm related genes and Influenza A. GO annotations related to this gene include transcription factor activity, sequence-specific DNA binding and signal transducer activity. An important paralog of this gene is NPAS2.