期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2013
卷号：110
期号：4
页码：E275-E284
DOI：10.1073/pnas.1219969110
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance StatementRhythmic mRNA expression is a hallmark of circadian rhythms. To address this regulation in Drosophila, we used high throughput sequencing to compare nascent RNA and mRNA levels in fly heads at different times of day. This indicated that some genes undergo rhythmic transcription with no impact on mRNA, whereas a few strongly rhythmic mRNAs have weak transcriptional oscillations. A substantial number of rhythmic genes manifest more robust mRNA cycling than transcriptional cycling, indicating that post-transcriptional regulation plays a widespread role in boosting circadian gene expression amplitude. Our study highlights the importance of directly assaying transcription to understand gene regulation. Rhythmic mRNA expression is a hallmark of circadian biology and has been described in numerous experimental systems including mammals. A small number of core clock gene mRNAs and a much larger number of output mRNAs are under circadian control. The rhythmic expression of core clock genes is regulated at the transcriptional level, and this regulation is important for the timekeeping mechanism. However, the relative contribution of transcriptional and posttranscriptional regulation to global circadian mRNA oscillations is unknown. To address this issue in Drosophila, we isolated nascent RNA from adult fly heads collected at different time points and subjected it to high-throughput sequencing. mRNA was isolated and sequenced in parallel. Some genes had cycling nascent RNAs with no cycling mRNA, caused, most likely, by light-mediated read-through transcription. Most genes with cycling mRNAs had significant nascent RNA cycling amplitudes, indicating a prominent role for circadian transcriptional regulation. However, a considerable fraction had higher mRNA amplitudes than nascent RNA amplitudes. The same comparison for core clock gene mRNAs gives rise to a qualitatively similar conclusion. The data therefore indicate a significant quantitative contribution of posttranscriptional regulation to mRNA cycling.
