Spatial patterning of P granules by RNA-induced phase separation of the intrinsically-disordered protein MEG-3

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Cite this article as: eLife 2016;5:e21337 doi: 10.7554/eLife.21337

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Abstract

RNA granules are non-membrane bound cellular compartments that contain RNA and RNA binding proteins. The molecular mechanisms that regulate the spatial distribution of RNA granules in cells are poorly understood. During polarization of the C. elegans zygote, germline RNA granules, called P granules, assemble preferentially in the posterior cytoplasm. We present evidence that P granule asymmetry depends on RNA-induced phase separation of the granule scaffold MEG-3. MEG-3 is an intrinsically disordered protein that binds and phase separates with RNA in vitro. In vivo, MEG-3 forms a posterior-rich concentration gradient that is anti-correlated with a gradient in the RNA-binding protein MEX-5. MEX-5 is necessary and sufficient to suppress MEG-3 granule formation in vivo, and suppresses RNA-induced MEG-3 phase separation in vitro. Our findings suggest that MEX-5 interferes with MEG-3's access to RNA, thus locally suppressing MEG-3 phase separation to drive P granule asymmetry. Regulated access to RNA, combined with RNA-induced phase separation of key scaffolding proteins, may be a general mechanism for controlling the formation of RNA granules in space and time.

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Jarrett Smith

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-6354-6551
Deepika Calidas

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

Competing interests
The authors declare that no competing interests exist.
Helen Schmidt

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-3449-2790
Tu Lu

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

Competing interests
The authors declare that no competing interests exist.
Dominique Rasoloson

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

Competing interests
The authors declare that no competing interests exist.
Geraldine Seydoux

Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States

For correspondence
gseydoux@jhmi.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-8257-0493

Funding

NIH Office of the Director (R01 HD37047)

Tu Lu

Howard Hughes Medical Institute

Geraldine Seydoux

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

Julie Ahringer, University of Cambridge, United Kingdom

Publication history

Received: September 7, 2016
Accepted: December 3, 2016
Accepted Manuscript published: December 3, 2016 (version 1)
Version of Record published: January 24, 2017 (version 2)

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.