In Vivo Role of Phosphorylation of Cryptochrome 2 in the Mouse Circadian Clock

Abstract

The circadian clock is finely regulated by posttranslational modifications of clock components. Mouse CRY2, a critical player in the mammalian clock, is phosphorylated at Ser557 for proteasome-mediated degradation, but its in vivo role in circadian organization was not revealed. Here, we generated CRY2(S557A) mutant mice, in which Ser557 phosphorylation is specifically abolished. The mutation lengthened free-running periods of the behavioral rhythms and PER2::LUC bioluminescence rhythms of cultured liver. In livers from mutant mice, the nuclear CRY2 level was elevated, with enhanced PER2 nuclear occupancy and suppression of E-box-regulated genes. Thus, Ser557 phosphorylation-dependent regulation of CRY2 is essential for proper clock oscillation in vivo.

ACKNOWLEDGMENTS

We thank Francis A. Stewart (Dresden University of Technology) for CAG-FLPe transgenic mice.

This work was supported in part by grants-in-aid for scientific research and by the Global COE program (Integrative Life Science Based on the Study of Biosignaling Mechanisms) from MEXT, Japan. A.H. and N.K. were supported by JSPS research fellowships for young scientists.