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Abstract
It has been proposed that the CLOCK-ARNTL (BMAL1) complex drives circadian transcription of thousands of genes, including Per and Cry family genes that encode suppressors of CLOCKARNTL-dependent transcription. However, recent studies demonstrated that 70-80% of circadian-oscillating mRNAs have no obvious rhythms in their de novo transcription4,5, indicating the potential importance of post-transcriptional regulation. Our CLOCK-ChIP-seq analysis identified rhythmic expression of adenosine deaminase, RNA-specific, B1 (Adarb1, also known as Adar2), an adenosine-to-inosine (A-to-I) RNA-editing enzyme. RNA-seq showed circadian rhythms of ADARBI-mediated A-to-I editing in a variety of transcripts. In Adarb1 -knockout mice, rhythms of large populations of mRNA were attenuated, indicating a profound impact of ADARBI-mediated A-to-I editing on RNA rhythms. Furthermore, Adarb1 -knockout mice exhibited short-period rhythms in locomotor activity and gene expression. These phenotypes were associated with abnormal accumulation of CRY2. The present study identifies A-to-I RNA editing as a key mechanism of post-transcriptional regulation in the circadian clockwork.