Exogenous messenger RNAs (mRNAs) require cellular machinery for delivery and translation but also encounter inhibitory factors. To investigate their regulation, we performed genome-wide CRISPR screens with in vitro–transcribed mRNAs in lipid … Exogenous messenger RNAs (mRNAs) require cellular machinery for delivery and translation but also encounter inhibitory factors. To investigate their regulation, we performed genome-wide CRISPR screens with in vitro–transcribed mRNAs in lipid … Science