RT Journal Article SR Electronic T1 Spatial patterning of P granules by RNA-induced phase separation of the intrinsically-disordered protein MEG-3 JF bioRxiv FD Cold Spring Harbor Laboratory SP 073908 DO 10.1101/073908 A1 Jarrett Smith A1 Deepika Calidas A1 Helen Schmidt A1 Tu Lu A1 Dominique Rasoloson A1 Geraldine Seydoux YR 2016 UL http://biorxiv.org/content/early/2016/09/07/073908.abstract AB 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 support a model whereby MEX-5 functions as an mRNA sink to locally suppress MEG-3 phase separation and drive P granule asymmetry.HIGHLIGHTS- The intrinsically-disordered protein MEG-3 is essential for localized assembly of P granules in C. elegans zygotes.- MEG-3 binds RNA and RNA stimulates MEG-3 phase separation.- The RNA-binding protein MEX-5 inhibits MEG-3 granule assembly in the anterior cytoplasm by sequestering RNA.