RNA–protein interactions in vivo: global gets specific

RNA-binding proteins (RBPs) impact every process in the cell; they act as splicing and polyadenylation factors, transport and localization factors, stabilizers and destabilizers, modifiers, and chaperones. RNA-binding capacity can be attributed to numerous protein domains that bind a limited repertoire of short RNA sequences. How is specificity achieved in cells? Here we focus on recent advances in determining the RNA-binding properties of proteins in vivo and compare these to in vitro determinations, highlighting insights into how endogenous RNA molecules are recognized and regulated. We also discuss the crucial contribution of structural determinations for understanding RNA-binding specificity and mechanisms.