Transcriptional regulatory logic of the diurnal cycle in the mouse liver

PLoS Biol. 2017 Apr 17;15(4):e2001069. doi: 10.1371/journal.pbio.2001069. eCollection 2017 Apr.

Abstract

Many organisms exhibit temporal rhythms in gene expression that propel diurnal cycles in physiology. In the liver of mammals, these rhythms are controlled by transcription-translation feedback loops of the core circadian clock and by feeding-fasting cycles. To better understand the regulatory interplay between the circadian clock and feeding rhythms, we mapped DNase I hypersensitive sites (DHSs) in the mouse liver during a diurnal cycle. The intensity of DNase I cleavages cycled at a substantial fraction of all DHSs, suggesting that DHSs harbor regulatory elements that control rhythmic transcription. Using chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq), we found that hypersensitivity cycled in phase with RNA polymerase II (Pol II) loading and H3K27ac histone marks. We then combined the DHSs with temporal Pol II profiles in wild-type (WT) and Bmal1-/- livers to computationally identify transcription factors through which the core clock and feeding-fasting cycles control diurnal rhythms in transcription. While a similar number of mRNAs accumulated rhythmically in Bmal1-/- compared to WT livers, the amplitudes in Bmal1-/- were generally lower. The residual rhythms in Bmal1-/- reflected transcriptional regulators mediating feeding-fasting responses as well as responses to rhythmic systemic signals. Finally, the analysis of DNase I cuts at nucleotide resolution showed dynamically changing footprints consistent with dynamic binding of CLOCK:BMAL1 complexes. Structural modeling suggested that these footprints are driven by a transient heterotetramer binding configuration at peak activity. Together, our temporal DNase I mappings allowed us to decipher the global regulation of diurnal transcription rhythms in the mouse liver.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ARNTL Transcription Factors / genetics
  • ARNTL Transcription Factors / metabolism
  • Animals
  • CLOCK Proteins / genetics
  • CLOCK Proteins / metabolism
  • Chromatin Immunoprecipitation
  • Circadian Clocks / genetics
  • Circadian Rhythm / genetics*
  • Deoxyribonuclease I / genetics
  • Deoxyribonuclease I / metabolism
  • Fasting
  • Gene Expression Regulation*
  • Liver / physiology*
  • Male
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Multiprotein Complexes / metabolism
  • Promoter Regions, Genetic
  • RNA Polymerase II / genetics
  • Transcription Factors / genetics
  • Transcription, Genetic

Substances

  • ARNTL Transcription Factors
  • Bmal1 protein, mouse
  • Multiprotein Complexes
  • Transcription Factors
  • CLOCK Proteins
  • Clock protein, mouse
  • RNA Polymerase II
  • Deoxyribonuclease I

Grants and funding

SystemsX http://www.systemsx.ch (grant number). This work was financed by CycliX, a grant from the Swiss SystemsX.ch (www.systemsx.ch) initiative evaluated by the Swiss National Science Foundation, Sybit, the SystemsX.chIT unit, the University of Lausanne, the University of Geneva, the Ecole Polytechnique Fédérale de Lausanne (EPFL), and Vital-IT. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.