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Cell. 2017 May 4;169(4):651-663.e14. doi: 10.1016/j.cell.2017.04.015.

Diurnal Oscillations in Liver Mass and Cell Size Accompany Ribosome Assembly Cycles.

Author information

1
Department of Molecular Biology, Sciences III, University of Geneva, iGE3, 1211 Geneva, Switzerland.
2
Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland.
3
Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; IMP - Research Institute of Molecular Pathology, Campus-Vienna-Biocenter 1, 1030 Vienna, Austria.
4
Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.
5
Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
6
Department of Diabetes and Circadian Rhythms, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland; School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland. Electronic address: frederic.gachon@rd.nestle.com.
7
Department of Molecular Biology, Sciences III, University of Geneva, iGE3, 1211 Geneva, Switzerland. Electronic address: ueli.schibler@unige.ch.

Abstract

The liver plays a pivotal role in metabolism and xenobiotic detoxification, processes that must be particularly efficient when animals are active and feed. A major question is how the liver adapts to these diurnal changes in physiology. Here, we show that, in mice, liver mass, hepatocyte size, and protein levels follow a daily rhythm, whose amplitude depends on both feeding-fasting and light-dark cycles. Correlative evidence suggests that the daily oscillation in global protein accumulation depends on a similar fluctuation in ribosome number. Whereas rRNA genes are transcribed at similar rates throughout the day, some newly synthesized rRNAs are polyadenylated and degraded in the nucleus in a robustly diurnal fashion with a phase opposite to that of ribosomal protein synthesis. Based on studies with cultured fibroblasts, we propose that rRNAs not packaged into complete ribosomal subunits are polyadenylated by the poly(A) polymerase PAPD5 and degraded by the nuclear exosome.

KEYWORDS:

TRAMP complex; cell size; circadian; diurnal; feeding-fasting rhythms; liver; mouse; rRNA degradation; rRNA polyadenylation; ribosomal protein synthesis

PMID:
28475894
PMCID:
PMC5570523
DOI:
10.1016/j.cell.2017.04.015
[Indexed for MEDLINE]
Free PMC Article

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