Control of sleep by a network of cell cycle genes

TARANIS Interacts with VRILLE and PDP1 to Modulate the Circadian Transcriptional Feedback Mechanism in Drosophila

The molecular clock that generates daily rhythms of behavior and physiology consists of interlocked transcription-translation feedback loops. In Drosophila, the primary feedback loop involving the CLOCK-CYCLE transcriptional activators and the PERIOD-TIMELESS transcriptional repressors is interlocked with a secondary loop involving VRILLE (VRI) and PAR DOMAIN PROTEIN 1 (PDP1), a repressor and activator of Clock transcription, respectively. Whereas extensive studies have found numerous transcriptional, translational, and posttranslational modulators of the primary loop, relatively little is known about the secondary loop. In this study, using male and female flies as well as cultured cells, we demonstrate that TARANIS (TARA), a Drosophila homolog of the TRIP-Br/SERTAD family of transcriptional coregulators, functions with VRI and PDP1 to modulate the circadian period and rhythm strength. Knocking down tara reduces rhythm amplitude and can shorten the period length, while overexpressing TARA lengthens the circadian period. Additionally, tara mutants exhibit reduced rhythmicity and lower expression of the PDF neuropeptide. We find that TARA can form a physical complex with VRI and PDP1, enhancing their repressor and activator functions, respectively. The conserved SERTA domain of TARA is required to regulate the transcriptional activity of VRI and PDP1, and its deletion leads to reduced locomotor rhythmicity. Consistent with TARA's role in enhancing VRI and PDP1 activity, overexpressing tara has a similar effect on the circadian period and rhythm strength as simultaneously overexpressing vri and Pdp1 Together, our results suggest that TARA modulates circadian behavior by enhancing the transcriptional activity of VRI and PDP1.

TARANIS interacts with VRILLE and PDP1 to modulate the circadian transcriptional feedback mechanism in Drosophila

The molecular clock that generates daily rhythms of behavior and physiology consists of interlocked transcription-translation feedback loops. In Drosophila, the primary feedback loop involving the CLOCK-CYCLE transcriptional activators and the PERIOD-TIMELESS transcriptional repressors is interlocked with a secondary loop involving VRILLE (VRI) and PAR DOMAIN PROTEIN 1 (PDP1), a repressor and activator of Clock transcription, respectively. Whereas extensive studies have found numerous transcriptional, translational, and post-translational modulators of the primary loop, relatively little is known about the secondary loop. In this study, using male and female flies as well as cultured cells, we demonstrate that TARANIS (TARA), a Drosophila homolog of the TRIP-Br/SERTAD family of transcriptional coregulators, functions with VRI and PDP1 to modulate the circadian period and rhythm strength. Knocking down tara reduces rhythm amplitude and can shorten the period length, while overexpressing TARA lengthens the circadian period. Additionally, tara mutants exhibit reduced rhythmicity and lower expression of the PDF neuropeptide. We find that TARA can form a physical complex with VRI and PDP1, enhancing their repressor and activator functions, respectively. The conserved SERTA domain of TARA is required to regulate the transcriptional activity of VRI and PDP1, and its deletion leads to reduced locomotor rhythmicity. Consistent with TARA's role in enhancing VRI and PDP1 activity, overexpressing tara has a similar effect on the circadian period and rhythm strength as simultaneously overexpressing vri and Pdp1. Together, our results suggest that TARA modulates circadian behavior by enhancing the transcriptional activity of VRI and PDP1.

Pumilio Regulates Sleep Homeostasis in Response to Chronic Sleep Deprivation in Drosophila melanogaster

Recent studies have identified the Drosophila brain circuits involved in the sleep/wake switch and have pointed to the modulation of neuronal excitability as one of the underlying mechanisms triggering sleep need. In this study we aimed to explore the link between the homeostatic regulation of neuronal excitability and sleep behavior in the circadian circuit. For this purpose, we selected Pumilio (Pum), whose main function is to repress protein translation and has been linked to modulation of neuronal excitability during chronic patterns of altered neuronal activity. Here we explore the effects of Pum on sleep homeostasis in Drosophila melanogaster, which shares most of the major features of mammalian sleep homeostasis. Our evidence indicates that Pum is necessary for sleep rebound and that its effect is more pronounced during chronic sleep deprivation (84 h) than acute deprivation (12 h). Knockdown of pum, results in a reduction of sleep rebound during acute sleep deprivation and the complete abolishment of sleep rebound during chronic sleep deprivation. Based on these findings, we propose that Pum is a critical regulator of sleep homeostasis through neural adaptations triggered during sleep deprivation.

The Neurobiological Basis of Sleep and Sleep Disorders

The functions of sleep remain a mystery. Yet they must be important since sleep is highly conserved, and its chronic disruption is associated with various metabolic, psychiatric, and neurodegenerative disorders. This review will cover our evolving understanding of the mechanisms by which sleep is controlled and the complex relationship between sleep and disease states.