title: An RNAi Screen To Identify Protein Phosphatases That Function Within the Drosophila Circadian Clock.
abstract: Circadian clocks in eukaryotes keep time via cell-autonomous transcriptional feedback loops. A well-characterized example of such a transcriptional feedback loop is in Drosophila, where CLOCK-CYCLE (CLK-CYC) complexes activate transcription of period (per) and timeless (tim) genes, rising levels of PER-TIM complexes feed-back to repress CLK-CYC activity, and degradation of PER and TIM permits the next cycle of CLK-CYC transcription. The timing of CLK-CYC activation and PER-TIM repression is regulated posttranslationally, in part through rhythmic phosphorylation of CLK, PER, and TIM. Previous behavioral screens identified several kinases that control CLK, PER, and TIM levels, subcellular localization, and/or activity, but two phosphatases that function within the clock were identified through the analysis of candidate genes from other pathways or model systems. To identify phosphatases that play a role in the clock, we screened clock cell-specific RNA interference (RNAi) knockdowns of all annotated protein phosphatases and protein phosphatase regulators in Drosophila for altered activity rhythms. This screen identified 19 protein phosphatases that lengthened or shortened the circadian period by ≥1 hr (p ≤ 0.05 compared to controls) or were arrhythmic. Additional RNAi lines, transposon inserts, overexpression, and loss-of-function mutants were tested to independently confirm these RNAi phenotypes. Based on genetic validation and molecular analysis, 15 viable protein phosphatases remain for future studies. These candidates are expected to reveal novel features of the circadian timekeeping mechanism in Drosophila that are likely to be conserved in all animals including humans.
authors: Department of Biology, Texas A&M University, College Station, Texas 77845-3258.|Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77845-3258.
authors: Parul
authors: P
authors: Agrawal
authors: Department of Biology, Texas A&M University, College Station, Texas 77845-3258 phardin@bio.tamu.edu.|Center for Biological Clocks Research, Texas A&M University, College Station, Texas 77845-3258.
authors: Paul E
authors: PE
authors: Hardin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D005820:Genetic Testing; D008297:Male; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D034622:RNA Interference; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; D010749:Phosphoprotein Phosphatases
keywords: Drosophila melanogaster; activity rhythms; circadian clocks; protein phosphatases