Subject(s)
Circadian Rhythm/genetics , DNA Repair/genetics , Deoxyribodipyrimidine Photo-Lyase/metabolism , Light , Phytochrome/metabolism , Amino Acid Sequence , Animals , Circadian Rhythm/radiation effects , DNA Repair/radiation effects , Deoxyribodipyrimidine Photo-Lyase/chemistry , Deoxyribodipyrimidine Photo-Lyase/genetics , Humans , Molecular Sequence Data , Phytochrome/chemistry , Phytochrome/genetics , Sequence Alignment , Sequence Homology, Amino AcidABSTRACT
Cryptochromes are photoactive pigments in the eye that have been proposed to function as circadian photopigments. Mice lacking the cryptochrome 2 blue-light photoreceptor gene (mCry2) were tested for circadian clock-related functions. The mutant mice had a lower sensitivity to acute light induction of mPer1 in the suprachiasmatic nucleus (SCN) but exhibited normal circadian oscillations of mPer1 and mCry1 messenger RNA in the SCN. Behaviorally, the mutants had an intrinsic circadian period about 1 hour longer than normal and exhibited high-amplitude phase shifts in response to light pulses administered at circadian time 17. These data are consistent with the hypothesis that CRY2 protein modulates circadian responses in mice and suggest that cryptochromes have a role in circadian photoreception in mammals.
Subject(s)
Circadian Rhythm/physiology , Drosophila Proteins , Eye Proteins , Flavoproteins/physiology , Light , Photoreceptor Cells, Invertebrate , Photoreceptor Cells, Vertebrate/physiology , Animals , Cell Cycle Proteins , Cryptochromes , Female , Flavoproteins/genetics , Gene Expression Regulation , Gene Targeting , In Situ Hybridization , Male , Mice , Mice, Inbred C57BL , Motor Activity , Mutation , Nuclear Proteins/genetics , Period Circadian Proteins , Receptors, G-Protein-Coupled , Suprachiasmatic Nucleus/metabolismABSTRACT
The putative blue-light photoreceptor genes of Arabidopsis thaliana and Sinapis alba (mustard) are highly homologous to the DNA repair genes encoding DNA photolyases. The photoreceptors from both organisms were overexpressed in Escherichia coli, purified, and characterized. The photoreceptors contain two chromophores which were identified as flavin adenine dinucleotide and methenyltetrahydrofolate. This chromophore composition suggests that the blue light photoreceptor may initiate signal transduction by a novel pathway which involves electron transfer. Despite the high degree of sequence identity to and identical chromophore composition with photolyases, neither photoreceptor has any photoreactivating activity.
