Abstract
Transcriptional regulation plays an important role in
Drosophila
melanogaster
circadian rhythms. The
period
promoter has been well studied, but the
timeless
promoter has not been analyzed in detail. Mutagenesis of the canonical E box in the
timeless
promoter reduces but does not eliminate
timeless
mRNA cycling or locomotor activity rhythms. This is because there are at least two other
cis
-acting elements close to the canonical E box, which can also be transactivated by the circadian transcription factor dCLOCK. These E-box-like sequences cooperate with the canonical E-box element to promote high-amplitude transcription, which is necessary for wild-type rhythmicity.