RIP-Seq of An Integrated Signaling Network Controls P-Bodies Dynamics and mRNA Translation in Human Glioblastoma
Processing (P)-bodies are cytoplasmic membrane-less condensates including translationally repressed mRNAs and proteins involved in the mRNA decay machinery. The mechanisms underlying P-bodies nucleation and mRNA decay have been largely described. However, the impact of signaling networks in P-bodies dynamics and mRNA translation is still not well understood. Here, we identify a ribonucleoprotein network assembled by the E3 ubiquitin ligase Praja2 at P-bodies that coordinates protein translation and mRNA turnover in human glioblastoma (GBM). Praja2 physically interacts and spatially colocalizes with the RNA helicase DDX6, a core component and nucleating factor of P-bodies.  Stimulation of the G protein-coupled receptor (GPCR)-cAMP pathway in GBM cells induces a non-proteolytic polyubiquitylation of DDX6 by Praja2. DDX6 ubiquitylation is required for P-bodies assembly and mRNA translation repression. Interfering with DDX6 ubiquitylation or downregulation of expression markedly affects P-bodies assembly. Moreover, genetic deletion of praja2 dramatically impacts the assembly of DDX6/mRNA complexes and the amount of translating polysomes, leading to cellular senescence and GBM growth arrest. These findings identify a cAMP-driven post-transcriptional control mechanism operating at P-bodies by the ubiquitin system that profoundly impacts on mRNA translation and cancer cell growth. This regulatory system may, thus, contribute to the adaptive metabolic rewiring underlying cancer growth and drug resistance.