A constitutively active cryptochrome in Drosophila melanogaster.

ABSTRACT

Light-activated cryptochrome (CRY) regulates circadian photoresponses in Drosophila melanogaster. Removing the carboxy (C) terminus to create CRYDelta produces, in yeast, a light-independent, constitutively active form. Here we show that flies overexpressing CRYDelta have a longer free-running period of locomotor activity, as well as altered cycling kinetics of the clock proteins timeless (TIM) and period (PER). Moreover, at the cellular level, they show a reduction in the level of TIM and in the nuclear localization of TIM and PER in two significant clusters of behavioral pacemaker cells the large and the small ventral lateral neurons (LN(v)s). These effects are similar to those seen in wild-type flies under continuous light and suggest a regulatory role for the C terminus of CRY on the photosensitive, photolyase-like part of the protein.