Transcriptional Regulation via Nuclear Receptor Crosstalk Required for the Drosophila Circadian Clock

Abstract

SummaryCircadian clocks in large part rely on transcriptional feedback loops. At the core of the clock machinery, the transcriptional activators CLOCK/BMAL1 (in mammals) and CLOCK/CYCLE (CLK/CYC) (in Drosophila) drive the expression of the period (per) family genes. The PER-containing complexes inhibit the activity of CLOCK/BMAL1 or CLK/CYC, thereby forming a negative feedback loop [1]. In mammals, the ROR and REV-ERB family nuclear receptors add positive and negative transcriptional regulation to this core negative feedback loop to ensure the generation of robust circadian molecular oscillation [2]. Despite the overall similarities between mammalian and Drosophila clocks, whether comparable mechanisms via nuclear receptors are required for the Drosophila clock remains unknown. We show here that the nuclear receptor E75, the fly homolog of REV-ERB α and REV-ERB β, and the NR2E3 subfamily nuclear receptor UNF are components of the molecular clocks in the Drosophila pacemaker neurons. In vivo assays in conjunction with the in vitro experiments demonstrate that E75 and UNF bind to per regulatory sequences and act together to enhance the CLK/CYC-mediated transcription of the per gene, thereby completing the core transcriptional feedback loop necessary for the free-running clockwork. Our results identify a missing link in the Drosophila clock and highlight the significance of the transcriptional regulation via nuclear receptors in metazoan circadian clocks.

TRAP-seq Profiling and RNAi-Based Genetic Screens Identify Conserved Glial Genes Required for Adult Drosophila Behavior

“…To our knowledge there is no evidence of local ecdysteroid synthesis in the fly nervous system, but receptors for the hormone (nuclear hormone receptors) are present in this tissue (Truman et al, 1994). Moreover, clock neurons themselves express ecdysteroid-responsive nuclear hormone receptors (e.g., UNF and E75), as well as a membrane ABC transporter (E23) postulated to regulate hormone responsiveness, and these are required for normal circadian rhythmicity (Itoh et al, 2011; Kumar et al, 2014; Jaumouillè et al, 2015). Evidence suggests that these factors serve as components of the molecular clock in Drosophila and more primitive insects (Kamae et al, 2014); they may respond to hormone to regulate specific genes, the molecular clock and behavior.…”

Conserved and Exapted Functions of Nuclear Receptors in Animal Development

“…The Drosophila E75 gene functions in molting, metamorphosis, oogenesis, and circadian rhythms [17,18]. It is essential for larval development, responding to ecdysone regulatory pathways at the onset of metamorphosis [19].…”

A Genome-Wide Identification and Analysis of the Basic Helix-Loop-Helix Transcription Factors in Brown Planthopper, Nilaparvata lugens

“…More specific, Sim and Trh control development of the central nervous system midline and the trachea, respectively [69,70,71]. Clk/ARNT heterodiner activates a feedback loop control the persistence and period of circadian rhythms [72,73]. It is known that NlMet mediates JH signal pathway and plays a role in the ovariole development and egg maturation of the brown planthopper [24], and it could likely be involved in resistance to insecticides [74,75].…”