Decoding post-transcriptional regulatory networks by RNA-linked CRISPR screening in human cells.

RNAs undergo a complex choreography of metabolic processes that are regulated by thousands of RNA-associated proteins. Here we introduce ReLiC, a scalable and high-throughput RNA-linked CRISPR approach to measure the responses of diverse RNA metabolic processes to knockout of 2,092 human genes encoding all known RNA-associated proteins. ReLiC relies on an iterative strategy to integrate genes encoding Cas9, single-guide RNAs (sgRNAs) and barcoded reporter libraries into a defined genomic locus. Combining ReLiC with polysome fractionation reveals key regulators of ribosome occupancy, uncovering links between translation and proteostasis. Isoform-specific ReLiC captures differential regulation of intron retention and exon skipping by SF3B complex subunits. Chemogenomic ReLiC screens decipher translational regulators upstream of messenger RNA (mRNA) decay and identify a role for the ribosome collision sensor GCN1 during treatment with the anti-leukemic drug homoharringtonine. Our work demonstrates ReLiC as a powerful framework for discovering and dissecting post-transcriptional regulatory networks in human cells.