Nuclear localization is required for function of the essential clock protein FRQ

Area of Science:

• Molecular biology
• Circadian rhythms
• Mycology

Background:

• The frequency (frq) gene in Neurospora is crucial for circadian rhythms.
• It forms a negative feedback loop with frq mRNA and FRQ protein.

Purpose of the Study:

• To investigate the role of nuclear localization of the FRQ protein in Neurospora's circadian oscillator.
• To determine if nuclear entry of FRQ is essential for its function in regulating circadian rhythmicity.

Main Methods:

• Deletion and reinsertion of the nuclear localization signal (NLS) in the FRQ protein.
• Observation of FRQ protein localization (cytoplasmic vs. nuclear).
• Assessment of circadian rhythmicity in modified Neurospora strains.

Main Results:

• FRQ protein is localized in the nucleus, and this is essential for its function.
• Deletion of the NLS prevents nuclear entry and abolishes circadian rhythms.
• Reinsertion of the NLS restores FRQ function and circadian rhythmicity.

Conclusions:

• Nuclear localization of FRQ is a critical step in the Neurospora circadian clock mechanism.
• FRQ enters the nucleus shortly after synthesis to regulate its own transcript levels.
• The study elucidates a key regulatory step in the molecular basis of circadian rhythms.