Casein kinase 1 dynamics underlie substrate selectivity and the PER2 circadian phosphoswitch

Area of Science:

• Molecular biology
• Chronobiology
• Biochemistry

Background:

• Post-translational control of PERIOD protein stability by Casein Kinase 1δ and ε (CK1) is crucial for metazoan circadian rhythms.
• CK1 is evolutionarily conserved, yet its regulation and substrate selectivity on PERIOD proteins remain poorly understood.
• Specific phosphorylation sites on PERIOD proteins directly influence the circadian period.

Purpose of the Study:

• To elucidate the regulatory mechanisms of CK1, focusing on factors influencing its substrate selectivity.
• To understand how CK1's activity is modulated to control circadian period length.
• To investigate the role of a conserved anion binding site in CK1's function.

Main Methods:

• Integrated experimental and computational approaches were employed.
• Studies focused on a conserved anion binding site within CK1 and its effect on the kinase activation loop.
• Analysis of period-altering mutations in CK1 from humans to Drosophila.

Main Results:

• A molecular switch involving a conserved anion binding site in CK1 was identified.
• This switch controls the conformation of the kinase activation loop, influencing PER2 phosphorylation.
• Allosteric linkage between two anion binding sites dynamically regulates CK1 activity and PER2 stability.
• Human and Drosophila mutations differentially modulated the switch, predictably altering PER2 stability.

Conclusions:

• The identified molecular switch provides a mechanism for CK1's regulation of circadian rhythms.
• Understanding this switch offers a foundation for manipulating CK1 activity to control circadian timing.
• This work deepens the understanding of how CK1 governs circadian clock function through PER2 regulation.