title: Spatial patterning of P granules by RNA-induced phase separation of the intrinsically-disordered protein MEG-3.
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 theC. eleganszygote, 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.
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Jarrett
authors.identifier: http://orcid.org/0000-0001-6354-6551
authors.initials: J
authors.lastname: Smith
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Deepika
authors.identifier: http://orcid.org/0000-0002-0859-5390
authors.initials: D
authors.lastname: Calidas
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Helen
authors.identifier: http://orcid.org/0000-0002-3449-2790
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Tu
authors.identifier: http://orcid.org/0000-0002-5697-300X
authors.initials: T
authors.lastname: Lu
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Dominique
authors.initials: D
authors.lastname: Rasoloson
authors.affiliation: Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
authors.forename: Geraldine
authors.identifier: http://orcid.org/0000-0001-8257-0493
authors.initials: G
authors.lastname: Seydoux
mesh_terms: D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D064267:Intrinsically Disordered Proteins / Q000378:metabolism*; D011485:Protein Binding; D012313:RNA / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D064267:Intrinsically Disordered Proteins; C000624325:MEG-3 protein, C elegans; C410587:MEX-5 protein, C elegans; D016601:RNA-Binding Proteins; D012313:RNA
keywords: C. elegans; MEG-3; MEX-5; P granules; RNA granules; cell biology; developmental biology; germline; phase separation; stem cells