Photoreceptors of the Xenopus laevis retina are the site of a circadian clock. As part of a differential display screen for rhythmic gene products in this system, we have identified a photoreceptor-specific mRNA expressed in peak abundance at night. cDNA cloning revealed an open reading frame encoding a putative 388 amino acid protein that we have named 'nocturnin' (for night- factor). This protein has strong sequence similarity to the C-terminal domain of the yeast transcription factor, CCR4, as well as a leucine zipper-like dimerization motif. Nocturnin mRNA levels exhibit a high amplitude circadian rhythm and nuclear run-on analysis indicates that it is controlled by the retinal circadian clock at the level of transcription. Our observations suggest that nocturnin may function through protein-protein interaction either as a component of the circadian clock or as a downstream effector of clock function.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Dec 10 1996|
ASJC Scopus subject areas