Learn More
Mutations in the period (per) gene of Drosophila melanogaster affect both circadian and ultradian rhythms. Levels of per gene product undergo circadian oscillation, and it is now shown that there is an underlying oscillation in the level of per RNA. The observations indicate that the cycling of per-encoded protein could result from per RNA cycling, and that(More)
Daily rhythms in behavior, physiology and metabolism are controlled by endogenous circadian clocks. At the heart of these clocks is a circadian oscillator that keeps circadian time, is entrained by environmental cues such as light and activates rhythmic outputs at the appropriate time of day. Genetic and molecular analyses in Drosophila have revealed(More)
The Drosophila circadian clock consists of two interlocked transcriptional feedback loops. In one loop, dCLOCK/CYCLE activates period expression, and PERIOD protein then inhibits dCLOCK/CYCLE activity. dClock is also rhythmically transcribed, but its regulators are unknown. vrille (vri) and Par Domain Protein 1 (Pdp1) encode related transcription factors(More)
Drosophila Clock (dClk) is rhythmically expressed, with peaks in mRNA and protein (dCLK) abundance early in the morning. dClk mRNA cycling is shown here to be regulated by PERIOD-TIMELESS (PER-TIM)-mediated release of dCLK- and CYCLE (CYC)-dependent repression. Lack of both PER-TIM derepression and dCLK-CYC repression results in high levels of dClk mRNA,(More)
To study the function of clock-gene-expressing neurons, the tetanus-toxin light chain (TeTxLC), which blocks chemical synaptic transmission, was expressed under the control of promoters of the clock genes period (per) and timeless (tim), each fused to GAL4-encoding sequences. Although TeTxLC did not affect cycling of a clock-gene product at the gross level,(More)
Transgenic flies carrying a 7.2 kb piece of DNA from the period (per) gene were analyzed for the presence of circadian locomotor activity rhythms and fluctuations of per-encoded mRNA and protein. The 5' end of this genomic fragment is within the first intron, which precedes the coding region. This promotorless fragment could rescue circadian behavioral(More)
The core mechanism of circadian timekeeping in arthropods and vertebrates consists of feedback loops involving several clock genes, including period (per) and timeless (tim). In the fruitfly Drosophila, circadian oscillations in per expression occur in chemosensory cells of the antennae, even when the antennae are excised and maintained in isolated organ(More)
In Drosophila melanogaster four circadian clock proteins termed PERIOD (PER), TIMELESS (TIM), dCLOCK (dCLK), and CYCLE (CYC/dBMAL1) function in a transcriptional feedback loop that is a core element of the oscillator mechanism. dCLK and CYC are members of the basic helix-loop-helix (bHLH)/PAS (PER-ARNT-SIM) superfamily of transcription factors and are(More)
Circadian fluctuations in per mRNA and protein are central to the operation of a negative feedback loop that is necessary for setting the free-running period and for entraining the circadian oscillator to light-dark cycles. In this study, per mRNA cycling and locomotor activity rhythms were measured under different light and dark cycling regimes to(More)
The organization of biological activities into daily cycles is universal in organisms as diverse as cyanobacteria, fungi, algae, plants, flies, birds and man. Comparisons of circadian clocks in unicellular and multicellular organisms using molecular genetics and genomics have provided new insights into the mechanisms and complexity of clock systems. Whereas(More)