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Proc Natl Acad Sci U S A. 2014 Dec 2;111(48):16995-7002. doi: 10.1073/pnas.1418963111. Epub 2014 Oct 31.

Analysis of clock-regulated genes in Neurospora reveals widespread posttranscriptional control of metabolic potential.

Author information

1
Department of Genetics, Geisel School of Medicine, Hanover, NH 03755;
2
US Department of Energy Joint Genome Institute, Walnut Creek, CA 94598;
3
Department of Biochemistry and Biophysics, Center of Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331;
4
Departments of Biomedical Engineering and Microbiology, Boston University, Boston, MA 02215;
5
Department of Biology, Texas A&M University, College Station, TX 77843; and.
6
Department of Genetics, Geisel School of Medicine, Hanover, NH 03755; Department of Biochemistry, Geisel School of Medicine, Hanover, NH 03755.
7
Department of Genetics, Geisel School of Medicine, Hanover, NH 03755; jay.c.dunlap@dartmouth.edu.

Abstract

Neurospora crassa has been for decades a principal model for filamentous fungal genetics and physiology as well as for understanding the mechanism of circadian clocks. Eukaryotic fungal and animal clocks comprise transcription-translation-based feedback loops that control rhythmic transcription of a substantial fraction of these transcriptomes, yielding the changes in protein abundance that mediate circadian regulation of physiology and metabolism: Understanding circadian control of gene expression is key to understanding eukaryotic, including fungal, physiology. Indeed, the isolation of clock-controlled genes (ccgs) was pioneered in Neurospora where circadian output begins with binding of the core circadian transcription factor WCC to a subset of ccg promoters, including those of many transcription factors. High temporal resolution (2-h) sampling over 48 h using RNA sequencing (RNA-Seq) identified circadianly expressed genes in Neurospora, revealing that from ∼10% to as much 40% of the transcriptome can be expressed under circadian control. Functional classifications of these genes revealed strong enrichment in pathways involving metabolism, protein synthesis, and stress responses; in broad terms, daytime metabolic potential favors catabolism, energy production, and precursor assembly, whereas night activities favor biosynthesis of cellular components and growth. Discriminative regular expression motif elicitation (DREME) identified key promoter motifs highly correlated with the temporal regulation of ccgs. Correlations between ccg abundance from RNA-Seq, the degree of ccg-promoter activation as reported by ccg-promoter-luciferase fusions, and binding of WCC as measured by ChIP-Seq, are not strong. Therefore, although circadian activation is critical to ccg rhythmicity, posttranscriptional regulation plays a major role in determining rhythmicity at the mRNA level.

KEYWORDS:

Neurospora; RNA-Seq; circadian; clock-controlled genes; transcription

PMID:
25362047
PMCID:
PMC4260557
DOI:
10.1073/pnas.1418963111
[Indexed for MEDLINE]
Free PMC Article

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