GSE110380
Proximity-CLIP provides a snapshot of occupied cis-acting elements on RNA in different subcellular compartments on a transcriptome-wide scale
Many cellular RNAs localize to specific subcellular compartments. Currently, methods to systematically study subcellular RNA localization are limited and lagging behind proteomic approaches. Here, we combined APEX2-mediated proximity biotinylation of proteins with PAR-CLIP to simultaneously profile the proteome and the transcriptome bound by RNA binding proteins in any given subcellular compartment. Our approach is fractionation-independent and does not rely on additional RNA manipulation and labeling steps, thus making it easy to apply. Furthermore, it enables to study the locali-zation of RNA processing intermediates, as well as the identification of regulatory RNA cis-acting elements occupied in different cellular compartments. In a proof-of-concept study we studied RNA and protein localization in the nucleus, cytoplasm and at cell-cell interfaces using Proximity-CLIP. These experiments revealed among other in-sights frequent transcriptional readthrough continuing for several kilobases down-stream of the canonical cleavage and polyadenylation site, a differential binding pat-tern of nuclear and cytoplasmic mRNAs, as well as the localization of mRNAs contain-ing 3'UTR CUG sequence elements at cell-cell interfaces, of which many encode regulatory proteins. Overall design: Proximity-CLIP takes advantage of the occupancy of cellular RNAs by RBPs throughout their life cycle. An APEX2 fusion protein is targeted to a cellular compartment, and cellular RNAs are labeled with 4SU. Cells are incubated with biotin-phenol (BP) for 30 min, before APEX2-mediated BP oxidation is activated by addition of hydrogen peroxide, followed by reaction quenching and 4SU-dependent protein-RNA crosslinking by UV illumination. BP radicals are created locally and either covalently tag proximate proteins or decay. Compartment-specific RNPs are captured by Streptavidin affinity chromatography. Eluted RNA is analyzed either by RNAse treatment followed by small RNA cDNA library preparation of RBP-protected footprints, analogous to PAR-CLIP, or by standard RNAseq. Data also includes RNAseq analysis of the input, i.e. total cell extract RNA prior to Streptavidin chromatography.