We have isolated three alleles of a novel Drosophila clock gene, double-time (dbt).
Short- (dbtS) and long-period (dbtL) mutants alter both behavioral rhythmicity and
molecular oscillations from previously identified clock genes, period and timeless.
A third allele, dbtP, causes pupal lethality and eliminates circadian cycling of per
and tim gene products in larvae. In dbtP mutants, PER proteins constitutively accumulate,
remain hypophosphorylated, and no longer depend on TIM proteins for their accumulation.
We propose that the normal function of DOUBLETIME protein is to reduce the stability
and thus the level of accumulation of monomeric PER proteins. This would promote a
delay between per/tim transcription and PER/TIM complex function, which is essential
for molecular rhythmicity.