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Rev-erbalpha2 mRNA encodes a stable protein with a potential role in circadian clock regulation.

Juliette Rambaud, Gerard Triqueneaux, Ingrid Masse, Bart Staels, Vincent Laudet, and Gerard Benoit (2009)

Mol Endocrinol, 23(5):630-9.

Circadian rhythms are observed in nearly all aspects of physiology and behavior.In mammals, such biological rhythms are supported by a complex network of self-sustained transcriptional loops and posttranslational modifications, which regulate timely controlled production and degradation of critical factors on a 24-h basis. Among these factors, the orphan nuclear receptor rev-erbalpha plays an essential role by linking together positive and negative regulatory loops. Asan essential part of the circadian core clock mechanism, REV-ERBalpha expressionshows a precisely scheduled oscillation reflecting the tight control of its production and degradation. In previous studies, we identified two alternative transcripts encoding two protein variants referred to as REV-ERBalpha1 and -alpha2. Interestingly, recent work identified structural elements present only in REV-ERBalpha1 that controls its turnover and thereby influences circadian oscillations. In the present work, we comparatively analyze the two variants andshow that REV-ERBalpha2 exhibits a half-life incompatible with a circadian function, suggesting that this variant exerts different biological functions. However, our comparative study clearly indicates undistinguishable DNA-binding properties and transcriptional repression activity as well as a similar regulation mechanism. The only consistent difference appears to be the relative expression level of the two transcripts, rev-erbalpha1 being one to 100 times more expressed than alpha2 depending on tissue and circadian time. Taking this finding into consideration, we reassessed REV-ERBalpha2 turnover and were able to show that this variant exhibits a reduced half-life when coexpressed with REV-ERBalpha1. We propose that the relative expression levels of the two REV-ERBalpha variants fine-tune the circadian period length by regulating REV-ERBalpha half-life.

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