Circadian Gene Expression in the Suprachiasmatic Nucleus

Circadian rhythms in mammals are orchestrated by a central clock in the suprachiasmatic nucleus (SCN). The clock emerges from cell-autonomous processes. Clock proteins cause the rhythmic expression of clock genes as well as output genes. Structural features and posttranslational modifications of clock proteins determine their intermolecular associations, subcellular localization, transcriptional activity, and stability. Some clock proteins positively and negatively regulate their own rhythmic expression via feedback on transcription. Patterns of clock gene expression within SCN cells and tissue are complex. The understanding of mammalian clock mechanisms critical to timekeeping is as yet incomplete.