E-box function in a period gene repressed by light.
In most organisms, light plays a key role in the synchronization of the circadian timing system with the environmental day-night cycle. Light pulses that phase-shift the circadian clock also induce the expression of period (per) genes in vertebrates. Here, we report the cloning of a zebrafish per gene, zfper4, which is remarkable in being repressed by light. We have developed an in vivo luciferase reporter assay for this gene in cells that contain a light-entrainable clock. High-definition bioluminescence traces have enabled us to accurately measure phase-shifting of the clock by light. We have also exploited this model to study how four E-box elements in the zfper4 promoter regulate expression. Mutagenesis reveals that the integrity of these four E-boxes is crucial for maintaining low basal expression together with robust rhythmicity and repression by light. Importantly, in the context of a minimal heterologous promoter, the E-box elements also direct a robust circadian rhythm of expression that is significantly phase-advanced compared with the original zfper4 promoter and lacks the light-repression property. Thus, these results reveal flexibility in the phase and light responsiveness of E-box-directed rhythmic expression, depending on the promoter context.
Vallone
Daniela
D
Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35-39, D-72076 Tübingen, Germany.
Gondi
Srinivas Babu
SB
Whitmore
David
D
Foulkes
Nicholas S
NS
D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics; D024721:E-Box Elements / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D008027:Light; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D056950:Period Circadian Proteins; D011401:Promoter Regions, Genetic; D014162:Transfection; D015027:Zebrafish / Q000235:genetics
D009687:Nuclear Proteins; D056950:Period Circadian Proteins