Light-dependent interaction between Drosophila CRY and the clock protein PER mediated by the carboxy terminus of CRY.
BACKGROUND
The biological clock synchronizes the organism with the environment, responding to changes in light and temperature. Drosophila CRYPTOCHROME (CRY), a putative circadian photoreceptor, has previously been reported to interact with the clock protein TIMELESS (TIM) in a light-dependent manner. Although TIM dimerizes with PERIOD (PER), no association between CRY and PER has previously been revealed, and aspects of the light dependence of the TIM/CRY interaction are still unclear.


RESULTS
Behavioral analysis of double mutants of per and cry suggested a genetic interaction between the two loci. To investigate whether this was reflected in a physical interaction, we employed a yeast-two-hybrid system that revealed a dimerization between PER and CRY. This was further supported by a coimmunoprecipitation assay in tissue culture cells. We also show that the light-dependent nuclear interactions of PER and TIM with CRY require the C terminus of CRY and may involve a trans-acting repressor.


CONCLUSIONS
This study shows that, as in mammals, Drosophila CRY interacts with PER, and, as in plants, the C terminus of CRY is involved in mediating light responses. A model for the light dependence of CRY is discussed.
Rosato
E
E
Department of Biology, University of Leicester, University Road, LE1 7RH, Leicester, United Kingdom. er6@le.ac.uk
Codd
V
V
Mazzotta
G
G
Piccin
A
A
Zordan
M
M
Costa
R
R
Kyriacou
C P
CP
D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002460:Cell Line; D002940:Circadian Rhythm / Q000502:physiology*; D056931:Cryptochromes; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D005136:Eye Proteins; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D019476:Insect Proteins / Q000378:metabolism; D008027:Light; D008124:Locomotion / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D017956:Photoreceptor Cells, Invertebrate; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D020798:Two-Hybrid System Techniques
D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D019476:Insect Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; C119828:cry protein, Drosophila; C096445:tim protein, Drosophila