Systematic detection of poly(A)(+) RNA-interacting proteins and their differential binding

RNA-binding proteins are dynamic posttranscriptional regulators of gene expression. Identification of mRNA-binding proteins in a given experimental setting is thus of great importance. We describe a procedure to enrich for direct poly(A)(+) RNA protein binders by 4-thiouridine-enhanced UV cross-linking and oligo(dT) purification. Subsequent nuclease-mediated release of RNA-binding proteins (RBPs) from mRNA allows for detection of eluted proteins by mass spectrometry. In addition, we provide a comparative approach to detect differences in RBP binding activity upon a biological stimulus.