CYCLE is a second bHLH-PAS clock protein essential for circadian rhythmicity and transcription of Drosophila period and timeless.
We report the identification, characterization, and cloning of another novel Drosophila clock gene, cycle (cyc). Homozygous cyc flies are completely arrhythmic. Heterozygous cyc/+ flies are rhythmic but have altered periods, indicating that the cyc locus has a dosage effect on period. The molecular circadian phenotype of homozygous cyc flies is like homozygous Clk flies presented in the accompanying paper: mutant flies have little or no transcription of the per and tim genes. Cloning of the gene indicates that it also encodes a bHLH-PAS transcription factor and is a Drosophila homolog of the human protein BMAL1. cyc is a nonsense mutation, consistent with its strong loss-of-function phenotype. We propose that the CYC:CLK heterodimer binds to per and tim E boxes and makes a major contribution to the circadian transcription of Drosophila clock genes.
Rutila
J E
JE
NSF, Center for Biological Timing, and Department of Biology, Brandeis University, Waltham, Massachusetts 02254, USA.
Suri
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Rosbash
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Hall
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D056930:ARNTL Transcription Factors; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001522:Behavior, Animal; D002874:Chromosome Mapping; D002940:Circadian Rhythm / Q000235:genetics*; D003001:Cloning, Molecular; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D018628:Gene Dosage; D017344:Genes, Insect; D018257:Helix-Loop-Helix Motifs; D019476:Insect Proteins / Q000096:biosynthesis*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis*; D056950:Period Circadian Proteins; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C538960:BMAL1 protein, human; C539040:PER protein, Drosophila; C112805:cyc protein, Drosophila; C096445:tim protein, Drosophila