Temperature sensing by the circadian clock

In the September 1 issue of G&D, Dr. Michael Brunner and colleagues have uncovered the molecular mechanism whereby temperature affects circadian patterns in the fungus Neurospora. The scientists investigated thermosensitive splicing of the central clockwork protein, FREQUENCY (FRQ), into both long (l) and short (s) isoforms depending upon temperature.

They found that at low temperatures, intron 6 of frq mRNA is preferentially spliced, resulting in the exclusion of the l-FRQ translation initiation site.

This mechanism works alongside a temperature-dependent inhibition of translation by uORFs to effectively modulate FRQ levels – and thereby circadian rhythmicity – with changes in ambient temperature.

Dr. Brunner emphasizes that the "interaction of molecular machinery with non-consensus signals - in this case the interaction of splicing machinery with non-consensus splice sites and the interaction of ribosomes with non-consensus translation initiation sites - may provide a general mechanism for temperature-sensing on the molecular level."

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