A conserved chronobiological complex times C. elegans development.

Area of Science:

• Chronobiology
• Developmental Biology
• Molecular Genetics

Background:

• The PAS-domain protein PERIOD (PER) is central to circadian rhythms in mammals.
• Its C. elegans orthologue, LIN-42, is implicated in developmental timing, but its molecular function is unclear.
• Understanding LIN-42 function could reveal evolutionary links between circadian and developmental timing systems.

Purpose of the Study:

• To elucidate the molecular mechanisms by which LIN-42 regulates developmental timing in C. elegans.
• To identify functional domains within LIN-42 and their interaction partners.
• To explore the evolutionary conservation of timing mechanisms between mammals and C. elegans.

Main Methods:

• Targeted deletion mutagenesis of LIN-42 in C. elegans.
• Biochemical assays to assess protein-protein interactions and kinase activity.
• In vivo studies of molting timing and subcellular localization of KIN-20.

Main Results:

• The PAS domains of LIN-42 are dispensable for regulating molt timing.
• A distinct conserved element, the CK1δ-binding domain (CK1BD), is essential for LIN-42 function in molting.
• The CK1BD mediates binding to KIN-20 (C. elegans CK1δ/ε orthologue), which phosphorylates LIN-42.
• Two helical motifs within the CK1BD (CK1BD-A and CK1BD-B) differentially regulate kinase binding and activity.
• Loss of LIN-42 binding alters KIN-20 subcellular localization, and both KIN-20 and the LIN-42 CK1BD are required for proper molt timing.

Conclusions:

• LIN-42 utilizes a CK1δ-binding domain (CK1BD) to regulate developmental timing, distinct from its PAS domains.
• The LIN-42-KIN-20 interaction is functionally conserved with the PER-CK1 complex in circadian timing.
• This study establishes LIN-42/PER and KIN-20/CK1δ/ε as a conserved signaling module for both circadian and developmental chronobiology.