Large-scale map of RNA binding protein interactomes across the mRNA life-cycle
RNA-binding proteins (RBPs) target RNA in a context-dependent manner to regulate gene expression. Protein-protein interaction (PPI) maps of RBP complexes and networks are critical for defining RBP function and RNA targeting. Yet, PPI networks under-represent RBP baits and need more information about RNA-driven interactions. Therefore, we generated an RNA-aware, RBP-interactome map combining two strategies that use systematic proteomic methods to identify 1) protein interactions using co-immunoprecipitation in the presence or absence of RNase treatment of a ~100 RBPs across the RNA life-cycle and 2) RNA-dependent complexes using Size Exclusion Chromatography. Together, this dataset provides proteome-wide, cell-type specific, and quantitative identification of RNA-protein interactions across multiple RNA processing events. In the resulting PPI network, several hundred database-supported interactions establish many complexes operating at each of these mRNA life-cycle stages. Nearly a thousand novel interactions imply new functions for RBPs across multiple steps of the RNA life cycle. Overlapping our network with eCLIP data, we find RNA targets between interactors and uncover complex-driven binding signatures. Betweenness-centrality scores identify multi-functional RBPs that participate across multiple mRNA life-cycle steps. We characterize the novel interactions and functions of different classes of multi-functional proteins. We find the scaffolding protein, ERH, interacts with numerous nuclear speckle proteins and facilitates splicing and mRNA export. Finally, we show that the splicing factor, SNRNP200, interacts with nuclear export, localization, and translation proteins and is an essential factor of RNA granule formation during stress. Our large-scale RBP interaction network provides new insights and a valuable resource for exploring new RBP complexes operating to control gene expression. Overall design: eCLIP-seq of human SNRNP200, CAPRIN, and G3BP1 eCLIP of RBP of interest. Each sample has an input and IP sample