Evidence item

To identify codon-dependent modifiers, we screen a targeted sgRNA library for genes that, when inactivated, increase the expression of rare versus common codon-enriched fluorescent reporters. This identifies the PAXT connection, a nuclear complex that targets transcripts to the exosome for degradation. Targeted loss of a PAXT component leads to a small but preferential increase in mRNA levels and stability and a more pronounced increase in protein expression of rare compared to common codon-enriched reporters. Transcriptomics coupled to proteomics further reveals that this leads to a preferential increase in the expression of endogenous proteins encoded by poorly expressed and long mRNAs specifically enriched in rare codons.