Molecular control of circadian behavioral rhythms

Area of Science:

• Chronobiology
• Molecular Biology
• Genetics

Background:

• Circadian rhythms are fundamental biological processes present across the animal kingdom.
• Key genes regulating circadian rhythms in Drosophila have conserved homologues in mammals, including humans.
• Molecular oscillations driven by gene products occur in specific brain cells of both Drosophila and mammals.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying circadian rhythm regulation.
• To investigate the conserved roles of period (PER) and timeless (TIM) genes and their protein products in circadian feedback loops.
• To understand how protein interactions and post-translational modifications influence the timing of gene transcription.

Main Methods:

• Analysis of gene transcription patterns for period and timeless.
• Investigation of PER and TIM protein accumulation, interaction, and nuclear translocation.
• Examination of the role of the double-time kinase in PER phosphorylation and degradation.

Main Results:

• PER and TIM proteins exhibit circadian transcription, with their nuclear localization inhibiting transcription factors dCLOCK and dBMAL1.
• PER and TIM must physically associate to enter the nucleus, a process delayed by the double-time kinase.
• The double-time kinase promotes PER degradation, but this is blocked upon PER complexation with TIM, prolonging transcription.

Conclusions:

• A conserved feedback loop involving PER and TIM proteins regulates circadian rhythms in animals.
• The timing of PER/TIM complex formation and nuclear entry is critical for maintaining circadian oscillations.
• Post-translational modification by the double-time kinase plays a key role in gating the circadian feedback loop.