CIPC is a mammalian circadian clock protein without invertebrate homologues

CIPC is a potent and specific inhibitor of CLOCK-BMAL1 activity in the circadian clock.

• CIPC shows circadian regulation across multiple tissues.
• CIPC functions independently of known negative regulators, PERs and CRYs.
• In vivo complexes of CIPC and CLOCK proteins have been identified.
• Depleting CIPC leads to a shortened circadian period length.
• CIPC is not related to any known proteins and lacks homologues outside of vertebrates.
• The findings indicate distinct pathways for negative feedback in the mammalian circadian clock.

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