Recruitment of mRNAs to P granules by gelation with intrinsically-disordered proteins

Abstract

Animals with germ plasm assemble cytoplasmic RNA granules (germ granules) that segregate with the embryonic germ lineage. How germ granules assemble and recruit RNA is not well understood. Here we characterize the assembly and RNA composition of the germ (P) granules of C. elegans. ~500 maternal mRNAs are recruited into P granules by a sequence independent mechanism that favors mRNAs with low ribosome coverage. Translational activation correlates temporally with P granule exit for two mRNAs that code for germ cell fate regulators. mRNAs are recruited into the granules by MEG-3, an intrinsically disordered protein that condenses with RNA to form nanoscale gels. Our observations reveal parallels between germ granules and stress granules and suggest that cytoplasmic RNA granules are reversible super-assemblies of nanoscale RNA-protein gel condensates.

Limited effects of m6A modification on mRNA partitioning into stress granules

“…This model also explains why length correlation with stress granule enrichment is a consistent metric in other cell types with different genes expressed (Khong et al, 2017; Namkoong et al, 2018). We suggest that this summative effect may be a general property of RNA targeting to RNP granules because length bias is also seen in the RNAs that accumulate in P-bodies (Matheny et al, 2019), P-granules (Lee et al, 2019), and BR-Bodies (Al-Husini et al, 2020). Therefore, like stress granules, no single individual protein-RNA interactions will substantially affect RNP granule partitioning.…”