Two novel doubletime mutants alter circadian properties and eliminate the delay between RNA and protein in Drosophila

Phosphorylation is an important feature of pacemaker organization inDrosophila. Genetic and biochemical evidence suggests involvement of the casein kinase I homologdoubletime(dbt) in theDrosophilacircadian pacemaker. We have characterized two noveldbtmutants. Both cause a lengthening of behavioral period and profoundly alterperiod(per) andtimeless(tim) transcript and protein profiles. The PER profile shows a major difference from the wild-type program only during the morning hours, consistent with a prominent role for DBT during the PER monomer degradation phase. The transcript profiles are delayed, but there is little effect on the protein accumulation profiles, resulting in the elimination of the characteristic lag between the mRNA and protein profiles. These results and others indicate that light and post-transcriptional regulation play major roles in defining the temporal properties of the protein curves and suggest that this lag is unnecessary for the feedback regulation ofperandtimprotein onperandtimtranscription.