Two new studies on circadian rhythms(sites on the FRQ clock protein across th...)

In Cell, the researchers suggest a new role for the clockassociated enzyme, casein kinase (CK)2 as a key control for temperature compensation. Pursuing two uncharacterized circadian protein mutants shown to affect compensation in an unusual way, the investigators identified different subunits of the same enzyme, CK2.

They developed new ways to manipulate the genome and showed, by controlling expression, that the level of CK2 dictates the form of compensation through the phosphorylation of the clock protein FRQ. The property is unique to CK2 and shared with none of the other similar enzymes implicated in clock function.

Coauthors in addition to Dunlap, professor of genetics and Loros, professor of biochemistry and of genetics, are Arun Mehra, Mi Shi, Christopher L. Baker, Hildur V. Colot.

The second study traced protein interactions throughout the cycles to demonstrate how phosphorylation controls circadian rhythm. Using a heavy isotope labeling method and quantitative mass spectrometry, the researchers pinpointed a near record number of modifications on FRQ and described how each appears and disappears over the day.

Moreover, their methods facilitated the identification of interacting proteins to track and correlate changes in the core circadian network. They determined the clusters and locations of known sites, and through mutational analysis identified novel functional domains to create a dynamic view of a clock protein in action.

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