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Table 1 Circadian clock genes and their functions in Drosophila and mice

From: From biological clock to biological rhythms

Organism Gene Protein function Clock function
Drosophila per Binds to dClk-Cyc as a heterodimer with Tim Inhibits dClk-Cyc-dependent transcription
  tim Stabilizes phosphorylated Per Contributes to delayed Per accumulation
   Promotes Per nuclear localization Acts with Per to inhibit dClk-Cyc-dependent transcription
   Binds to dClk-Cyc as a heterodimer with Per Mediates phase-resetting in response to light
   Degraded in response to light  
  dClk Forms a heterodimeric complex with Cyc Activates per and tim transcription and inhibits dClk transcription
  Cyc (Bmal1) Forms a heterodimeric complex with dClk Activates per and tim transcription and inhibits dClk transcription
  dbt (CK1ε) Phosphorylates Per Destabilizes Per
  cry Photoreceptor element that binds to Tim Initiates light signaling required for phase resetting
Mouse mPer1 Interacts with Clock-Bmal1? Moderate inhibition of Clock-Bmal1-dependent transcription
  mPer2 Interacts with Clock-Bmal1? Activation of Bmal1 transcription
    Moderate inhibition of Clock-Bmal1-dependent transcription
  mPer3 Interacts with Clock-Bmal1? Moderate inhibition of Clock-Bmal1-dependent transcription
  mTim Interacts with Clock-Bmal1? Moderate inhibition of Clock-Bmal1-dependent transcription
  Clock Forms a heterodimeric complex with Bmal1 Activates mPer1-3 and mCry1
  Bmal1 Forms a heterodimeric complex with Clock Activates mPer1-3 and mCry1
  CK1ε (tau) Phosphorylates mPer1 and mPer2 Destabilizes mPers
  mCry1 Dimerizes with mPer1-3 Strongly inhibits Clock-Bmal1-dependent transcription
   Binds to Clock-Bmal1  
   Promotes mPer1-3 nuclear localization  
  mCry2 Dimerizes with mPer1-3 Strongly inhibits Clock-Bmal1-dependent transcription
   Binds to Clock-Bmal1  
   Promotes mPer1-3 nuclear localization  
  1. Gene symbols are as described in the text. Protein functions are derived from in vivo and/or in vitro experiments. Clock function is derived from mutant phenotypes and/or in vivo experiments. The '?' for mPer1-3 and mTim protein function indicates that the indicated activity is presumed on the basis of the clock function of these proteins. Cyc is the Drosophila homolog of mouse Bmal1 and dbt is the homolog of mouse CK1ε and hamster tau.