page_title: Vrille (gene)
section_title: Circadian
hierarchical_section_title: Vrille (gene) / Function / Circadian
caption_attribution_description: English: Interlocked molecular feedback loops in Drosophila melanogaster. CLOCK/CYCLE heterodimer acts as transcriptional activator (positive element) for period (per) and timeless (tim) genes. The heterodimer of PER/TIM is phosphorylated in the cytoplasm in the presence of specific kinases, and the phosphorylated complex then acts as inhibitor for its own transcription (negative element). The VRI and PDP1 proteins regulate the levels of CLK/CYC complex, which in turn are regulated by CLK/CYC. Thus, CLK/CYC heterodimer appears to be an important component that connects the two loops and is important for sustaining molecular oscillations. The protein Cryptochrome (CRY) has been implicated in the light entrainment pathways of the Drosophila molecular clock.
context_page_description: Vrille is a bZIP transcription factor found on chromosome 2 in Drosophila melanogaster. Vrille mRNA and protein product oscillate predictably on a 24-hour timescale and interact with other circadian clock genes to regulate circadian rhythms in Drosophila. It is also a regulator in embryogenesis; it is expressed in multiple cell types during multiple stages in development, coordinating embryonic dorsal/ventral polarity, wing-vein differentiation, and ensuring tracheal integrity. It is also active in the embryonic gut but the precise function there is unknown. Mutations in vri alter circadian period and cause circadian arrhythmicity and developmental defects in Drosophila.
context_section_description: The current model of the Drosophila circadian oscillator is composed of two interlocking transcription/translation negative feedback loops. One loop consists of per, tim, clk, cyc, and their mRNA and protein products. In this loop, the PER/TIM heterodimer is a repressor for the CLK/CYC complex while the CLK/CYC complex serves as an activator and transcription factor for per and tim. Vrille is activated by the CLK/CYC complex and encodes a repressor of CLK transcription. The second regulatory loop is composed of vri, pdp1, clk, and their mRNA and protein products. Vrille is activated by the CLK/CYC complex and encodes a repressor of CLK transcription. High levels of CLK/CYC activate the transcription of Vrille mRNA to increase protein production, leading to transcriptional repression of clk which ultimately reduces the concentration of CLK/CYC complexes. Lastly, PDP1 protein, a bZIP transcription factor, serves as an activator of clk transcription and peaks 3–6 hours after the VRI protein peak and, together with VRI, regulate daily rhythms in CLK protein.
caption: Interlocked molecular feedback loops in Drosophila melanogaster. CLOCK/CYCLE heterodimer acts as transcriptional activator (positive element) for period (per) and timeless (tim) genes. The heterodimer of PER/TIM is phosphorylated in the cytoplasm in the presence of specific kinases, and the phosphorylated complex then acts as inhibitor for its own transcription (negative element). The VRI and PDP1 proteins regulate the levels of CLK/CYC complex, which in turn are regulated by CLK/CYC. Thus, CLK/CYC heterodimer appears to be an important component that connects the two loops and is important for sustaining molecular oscillations. The protein Cryptochrome (CRY) has been implicated in the light entrainment pathways of the Drosophila molecular clock.
exif: {}