Two new studies on circadian rhythms( Hanover NHDartmouth Medical School g...)

Hanover, NHDartmouth Medical School geneticists have made new inroads into understanding the regulatory circuitry of the biological clock that synchronizes the ebb and flow of daily activities, according to two studies published May 15.

Research on the relationship between clocks and temperature, reported in Cell, offers insight into a longstanding puzzle of temperature compensation: why the 24-hour circadian rhythm does not change with temperature when metabolism is so affected.

A related study, in Molecular Cell, tracks a clock protein in action, mapping hundreds of highly choreographed modifications and interactions to provide the first complete view of regulation across a day.

The new work adds clarity to the molecular underpinnings of circadian clocks, the finely tuned cellular timekeepers that drive most organisms. Circadian systems are biological oscillators that orchestrate activities through an elaborate network of interactive proteins and feedback loops. All clocks rely on transfer of phosphate groups, called phosphorylation, to clock proteins for setting the 24-hour cycle.

Both studies looked at phosphorylation of the frequency (FRQ) clock protein, a central feedback cog in the fungal clock system. They build on the research of team leaders, Drs. Jay Dunlap and Jennifer Loros, who have documented the workings of FRQ and most other components in the Neurospora clock.

"The Cell paper describes how the cell uses phosphorylation of a clock protein to keep the period length of the cycle close to the same across a range of temperatures. This phenomenon, called temperature compensation, is one of the few canonical properties of rhythms that still lack molecular description," said Dunlap.

"The one in Molecular Cell describes collaborative work with Dr. Scott Gerber in the Norris Cotton Cancer Center. We used mass spectrometry to follow the degree of phosphorylation of over 75
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