title: PRD-1, a Component of the Circadian System of Neurospora crassa, Is a Member of the DEAD-box RNA Helicase Family.
abstract: The circadian rhythms found in almost all organisms are driven by molecular oscillators, including transcription/translation feedback loops (TTFLs). However, TTFL-independent oscillators can drive rhythms in both eukaryotes and prokaryotes. The fungus Neurospora crassa is a model organism for studying the molecular mechanism of the circadian clock. Although a circadian TTFL involving the proteins FRQ, WC-1, and WC-2 is well-characterized in N. crassa, rhythms can still be observed in the absence of this feedback loop. These rhythms are said to be driven by 1 or more FRQ-less oscillator(s) (FLOs). The prd-1 mutation lengthens the period in frq wild type and was previously shown to severely disrupt FRQ-less rhythms in frq null mutants under several different conditions; therefore, the prd-1 gene product is a candidate for a component of a FLO. We report here that prd-1 also disrupts free-running rhythms in wc-1 null mutants, confirming its effects on FRQ-less rhythms. We have now mapped and identified the prd-1 gene as NCU07839, a DEAD-box RNA helicase dbp-2 Complementation with the wild-type gene corrects the rhythm defects of the prd-1 mutant in the complete circadian system (when the FRQ-based TTFL is intact) and also the free-running FRQ-less rhythm on low choline. A PRD-1-GFP fusion protein localizes to the nucleus. The prd-1 mutant has a single base pair change in the first base of an intron that results in abnormally spliced transcripts. FRQ-less rhythms on low choline, or entrained to heat pulses, were only marginally affected in strains carrying deletions of 2 other RNA helicases (prd-6 and msp-8). We conclude that PRD-1 is a member of an RNA helicase family that may be specifically involved in regulating rhythmicity in N. crassa in both the complete circadian system and FLO(s).
authors.forename: Keyur
authors.initials: K
authors.lastname: Adhvaryu
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Firoozi
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario M5T 1R4, Canada.
authors.forename: Kamyar
authors.initials: K
authors.lastname: Motavaze
authors.forename: Patricia
authors.initials: P
authors.lastname: Lakin-Thomas
mesh_terms: D057906:Circadian Clocks; D002940:Circadian Rhythm; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism*; D025461:Feedback, Physiological; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005816:Genetic Complementation Test; D005838:Genotype; D009154:Mutation; D009492:Neurospora crassa / Q000201:enzymology / Q000235:genetics*; D014176:Protein Biosynthesis; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D005656:Fungal Proteins; D053487:DEAD-box RNA Helicases
keywords: DDX5; FRQ-less oscillator; Neurospora; circadian; dbp-2; helicase; prd-1