Thermally regulated translational control of FRQ mediates aspects of temperature responses in the neurospora circadian clock.
Two forms of FRQ, a central component of the Neurospora circadian clock, arise through alternative in-frame initiation of translation. Either form alone suffices for a functional clock at some temperatures, but both are always necessary for robust rhythmicity. Temperature regulates the ratio of FRQ forms by favoring different initiation codons at different temperatures; when either initiation codon is eliminated, the temperature range permissive for rhythmicity is demonstrably reduced. This temperature-influenced choice of translation-initiation site represents a novel adaptive mechanism that extends the physiological temperature range over which clocks function. Additionally, a temperature-dependent threshold level of FRQ is required to establish the feedback loop comprising the oscillator. These data may explain how temperature limits permissive for rhythmicity are established, thus providing a molecular understanding for a basic characteristic of circadian clocks.
Liu
Y
Y
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844, USA.
Garceau
N Y
NY
Loros
J J
JJ
Dunlap
J C
JC
D001683:Biological Clocks / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics*; D018387:Codon, Initiator / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D007536:Isomerism; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D009491:Neurospora / Q000737:chemistry / Q000235:genetics*; D014176:Protein Biosynthesis / Q000502:physiology*; D013696:Temperature
D018387:Codon, Initiator; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins