Period2 3'-UTR and microRNA-24 regulate circadian rhythms by repressing PERIOD2 protein accumulation.

ABSTRACT

We previously created two PER2LUCIFERASE (PER2LUC) circadian reporter knockin mice that differ only in the Per2 3'-UTR region Per2Luc, which retains the endogenous Per2 3'-UTR and Per2LucSV, where the endogenous Per2 3'-UTR was replaced by an SV40 late poly(A) signal. To delineate the in vivo functions of Per2 3'-UTR, we analyzed circadian rhythms of Per2LucSV mice. Interestingly, Per2LucSV mice displayed more than threefold stronger amplitude in bioluminescence rhythms than Per2Luc mice, and also exhibited lengthened free-running periods (∼24.0 h), greater phase delays following light pulse, and enhanced temperature compensation relative to Per2Luc Analysis of the Per2 3'-UTR sequence revealed that miR-24, and to a lesser degree miR-30, suppressed PER2 protein translation, and the reversal of this inhibition in Per2LucSV augmented PER2LUC protein level and oscillatory amplitude. Interestingly, Bmal1 mRNA and protein oscillatory amplitude as well as CRY1 protein oscillation were increased in Per2LucSV mice, suggesting rhythmic overexpression of PER2 enhances expression of Per2 and other core clock genes. Together, these studies provide important mechanistic insights into the regulatory roles of Per2 3'-UTR, miR-24, and PER2 in Per2 expression and core clock function.