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

Abstract

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