Molecular analysis of zebrafish photolyase/cryptochrome family: two types of cryptochromes present in zebrafish.
BACKGROUND
Cryptochromes (CRY), members of the DNA photolyase/cryptochrome protein family, regulate the circadian clock in animals and plants. Two types of animal CRYs are known, mammalian CRY and Drosophila CRY. Both CRYs participate in the regulation of circadian rhythm, but they have different light dependencies for their reactions and have different effects on the negative feedback loop which generates a circadian oscillation of gene expression. Mammalian CRYs act as a potent inhibitor of transcriptional activator whose reactions do not depend on light, but Drosophila CRY functions as a light-dependent suppressor of transcriptional inhibitor.


RESULTS
We cloned seven zebrafish genes that carry members of the DNA photolyase/cryptochrome protein family; one (6-4)photolyase and six cry genes. A sequence analysis and determination of their in vitro functions showed that these zebrafish cry genes constitute two groups. One has a high sequence similarity to mammalian cry genes and inhibits CLOCK:BMAL1 mediated transcription. The other, which has a higher sequence similarity to the Drosophila cry gene rather than the mammalian cry genes, does not carry transcription inhibitor activity. The expressions of these cry genes oscillate in a circadian manner, but their patterns differ.


CONCLUSIONS
These findings suggest that functionally diverse cry genes are present in zebrafish and each gene has different role in the molecular clock.
Kobayashi
Y
Y
Radiation Biology Center, Kyoto University, Yoshidakonoe-cho, Sakyoku, Kyoto 606-8501 Japan.
Ishikawa
T
T
Hirayama
J
J
Daiyasu
H
H
Kanai
S
S
Toh
H
H
Fukuda
I
I
Tsujimura
T
T
Terada
N
N
Kamei
Y
Y
Yuba
S
S
Iwai
S
S
Todo
T
T
D056930:ARNTL Transcription Factors; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001683:Biological Clocks; D015152:Blotting, Northern; D056926:CLOCK Proteins; D002940:Circadian Rhythm; D017124:Conserved Sequence; D056931:Cryptochromes; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D019143:Evolution, Molecular; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017440:Photoperiod; D017956:Photoreceptor Cells, Invertebrate; D010802:Phylogeny; D043562:Receptors, G-Protein-Coupled; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D014466:Ultraviolet Rays; D015027:Zebrafish / Q000235:genetics* / Q000378:metabolism
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D056931:Cryptochromes; D004255:Deoxyribodipyrimidine Photo-Lyase; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators; D014157:Transcription Factors; C119828:cry protein, Drosophila; C098727:pyrimidine(6-4)pyrimidone photolyase