Abstract
cAMP response element-binding protein (CREB) and nuclear factor kappa-B (NF-κB) are two ubiquitous transcription factors involved in a wide number of cellular processes, including the circadian system. Many previous studies on these factors use cellular assays that provide limited information on circadian activity or anatomical specificity. The ability to study transcription factors in defined tissue within intact animals will help to bridge the gap between cellular and in vivo data. We have used the GAL4-UAS and FLP-FRT systems to gain spatial control over reporter gene expression. Using a luciferase-based reporter, we show in vivo that Drosophila dCREB2- and NF-κB-mediated transcription oscillates in neuronal cells, glia, and in the mushroom body, a higher-order brain center in flies. This oscillation is under circadian control, cycling with a 24-hour rhythm, under both light-dark and dark-dark conditions. In light-light conditions, dCREB2 and NF-κB reporter flies exhibit a suppression of rhythmic activity. Furthermore, neuronal cycling of dCREB2 and NF-κB activity are modulated in period mutant flies, indicating these oscillations are controlled through the central clock. This study shows for the first time region-specific circadian oscillation of dCREB2/NF-κB activity in the Drosophila nervous system.
Highlights
The biological importance of circadian rhythms is firmly established and widely accepted
We focus on two ubiquitous transcription factor families that have been linked to the circadian system: cAMP response elementbinding protein (CREB) and nuclear factor kappa-B (NF-kB)
We provide evidence in vivo that both dCREB2 and NF-kB transcriptional activities oscillate in multiple subsets of cells in the Drosophila nervous system
Summary
The biological importance of circadian rhythms is firmly established and widely accepted. Once accumulation of cytoplasmic PER and TIM proteins is sufficient, they enter the nucleus and inhibit CLK/CYC, inhibiting transcriptional activity The presence of these molecular oscillators in a subset of clock cells is sufficient to drive rhythmic responses throughout the organism [3]. Luciferase-based transcription factor reporters have provided significant insight into the function and regulation of the molecular clock [27,28,29,30,31,32,33]. Despite the advantages of this approach, it has rarely been applied outside of the core molecular clock to measure the general activity of transcription factors over the day:night cycle. We provide evidence in vivo that both dCREB2 and NF-kB transcriptional activities oscillate in multiple subsets of cells in the Drosophila nervous system. That these oscillations are under circadian control, and are modulated in per mutant flies
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