CK2 and DBT promote temperature compensation of the Drosophila circadian clock via distinct pathways

Circadian rhythms are defined by three fundamental properties: they are self-sustained, entrained by environmental cues, and temperature compensated. The molecular basis of temperature compensation remains incompletely understood. Here, we found that reducing the activity of two highly conserved circadian kinases, Drosophila doubletime /casein kinase 1 and casein kinase 2 (DBT/CK1 and CK2), compromises temperature compensation in Drosophila melanogaster . Genetic analyses indicate that DBT and CK2 promote temperature compensation through distinct but additive pathways. DBT works through the per Short phosphorylation cluster and the Ser47 phosphodegron of the core clock protein PER, whereas CK2 acts through a phosphocluster in TIM and PER Ser45 residue. Simultaneous disruption of both pathways results in hyperphosphorylated PER accumulation and impaired PER clearance from circadian pacemaker neuron nuclei. Combined with previous studies, our findings support a central role for nuclear PER phosphorylation dynamics in buffering circadian period against environmental temperature fluctuations.