Molecular analysis of zebrafish photolyase/cryptochrome family: two types of cryptochromes present in zebrafish

Sep 6, 2000Genes to cells : devoted to molecular & cellular mechanisms

Molecular study of light-sensitive proteins in zebrafish: two types of cryptochromes found

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Abstract

Seven zebrafish genes related to the DNA photolyase/cryptochrome protein family were cloned.

One gene (6-4)photolyase and six cry genes were identified in zebrafish.
Zebrafish cry genes can be categorized into two groups based on their sequence similarity.
One group resembles mammalian cry genes and inhibits CLOCK:BMAL1 mediated transcription.
The other group, more similar to Drosophila cry genes, does not inhibit transcription.
All identified cry genes exhibit circadian oscillation in expression, but with differing patterns.

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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.

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Molecular analysis of zebrafish photolyase/cryptochrome family: two types of cryptochromes present in zebrafish

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