title: The molecular workings of the Neurospora biological clock.
abstract: In Neurosporacrassa the FRQ/WC feedback loop has been shown to be central to the function of the circadian clock. Similar to other eukaryotic systems it is based on a transcription-translation PAS heterodimer type feedback. FRQ levels cycle with a period identical to that of the Neurospora circadian cycle and its expression is rapidly induced by light. A complex of White Collar 1 (WC-1) and White Collar 2 (WC-2) (the WCC) is required for the transcriptional activation of frq. The oscillation in frq message is transcriptionally regulated via a single necessary and sufficient cis-acting element in the frq promoter, the Clock-Box (CB) bound by WCC. Light-induction of frq transcription is mediated by WCC binding to two cis-acting elements (LREs) in the frq promoter. WC-1, with flavin adenine dinucleotide (FAD) as a cofactor, is the blue-light photoreceptor. The original description of a frq-null strain, frq9, (Loros et al 1986) included a description of oscillations in asexual conidial banding that occasionally appeared following 3 to 7 days of arrhythmic development now referred to as FLO for FRQ-less oscillator. Unlike the intact clock, FLO period is sensitive to media composition. We have identified a circadianly regulated gene whose mutation interferes with FLO even under temperature entrainment conditions. This same mutation affects the circadian clock in a frq+ background causing a shorter period length as well as temperature response defects. This gene may be an entry point to study the connection between the biological clock and other basic cellular mechanisms.
authors.affiliation: Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.
authors.forename: Allan C
authors.initials: AC
authors.lastname: Froehlich
authors.forename: Antonio
authors.initials: A
authors.lastname: Pregueiro
authors.forename: Kwangwon
authors.initials: K
authors.lastname: Lee
authors.forename: Deanna
authors.initials: D
authors.lastname: Denault
authors.forename: Hildur
authors.initials: H
authors.lastname: Colot
authors.forename: Minou
authors.initials: M
authors.lastname: Nowrousian
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Loros
authors.forename: Jay C
authors.initials: JC
authors.lastname: Dunlap
mesh_terms: D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology* / Q000528:radiation effects; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D005800:Genes, Fungal; D008027:Light; D008954:Models, Biological; D009492:Neurospora crassa / Q000235:genetics* / Q000502:physiology* / Q000528:radiation effects; D020283:Photoreceptors, Microbial / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D013696:Temperature
chemical_list: D005656:Fungal Proteins; D020283:Photoreceptors, Microbial