Huang, R. et al. Proc. Natl. Acad. Sci. USA 115, E3879–E3887 (2018).

Post-transcriptional gene regulation is in large part driven by the proteins associated with RNAs, and thus it is of great interest to establish a comprehensive catalog of RNA-binding proteins (RBPs). Huang et al. developed CARIC (click chemistry–assisted RNA interactome capture) for unbiased RBP profiling. The method begins with metabolic labeling of RNA to incorporate an alkyne-containing uridine analog (EU) and a photoactivatable thio-uridine (4SU). Upon UV light exposure, proteins bound to RNAs are cross-linked to 4SU, and azide–biotin is clicked onto EU to provide a handle by which the RNA can be enriched. After digestion of the RNA and mass-spectrometry-based protein identification, the researchers obtained a list of nearly 600 RBPs from HeLa cells that included 130 proteins not known to associate with RNA. CARIC can be applied to any cell type and will enrich RBPs across all RNAs, independent of their polyadenylation status.