Redundant Function of REV-ERBα and β and Non-Essential Role for Bmal1 Cycling in Transcriptional Regulation of Intracellular Circadian Rhythms

作者：Andrew C. Liu, Hien Tran, Eric Erquan Zhang, Aaron A. Priest, David K. Welsh, Steve A. Kay · 发表于：PLoS Genetics · 年份：2008 · DOI：10.1371/journal.pgen.1000023 · 被引用次数：408 · 研究领域：Circadian rhythm and melatonin、Genetics, Aging, and Longevity in Model Organisms、Neurobiology and Insect Physiology Research

The mammalian circadian clockwork is composed of a core PER/CRY feedback loop and additional interlocking loops. In particular, the ROR/REV/Bmal1 loop, consisting of ROR activators and REV-ERB repressors that regulate Bmal1 expression, is thought to "stabilize" core clock function. However, due to functional redundancy and pleiotropic effects of gene deletions, the role of the ROR/REV/Bmal1 loop has not been accurately defined. In this study, we examined cell-autonomous circadian oscillations using combined gene knockout and RNA interference and demonstrated that REV-ERBalpha and beta are functionally redundant and are required for rhythmic Bmal1 expression. In contrast, the RORs contribute to Bmal1 amplitude but are dispensable for Bmal1 rhythm. We provide direct in vivo genetic evidence that the REV-ERBs also participate in combinatorial regulation of Cry1 and Rorc expression, leading to their phase-delay relative to Rev-erbalpha. Thus, the REV-ERBs play a more prominent role than the RORs in the basic clock mechanism. The cellular genetic approach permitted testing of the robustness of the intracellular core clock function. We showed that cells deficient in both REV-ERBalpha and beta function, or those expressing constitutive BMAL1, were still able to generate and maintain normal Per2 rhythmicity. Our findings thus underscore the resilience of the intracellular clock mechanism and provide important insights into the transcriptional topologies underlying the circadian clock...