Human DHX29 detects nonoptimal codon usage to regulate mRNA stability

Synonymous codon usage controls global gene expression in both prokaryotic and eukaryotic species. Nonoptimal codons are known to induce messenger RNA (mRNA) decay; however, the underlying molecular mechanism remains poorly understood in human cells. Through genome-wide CRISPR screening, we identified the RNA binding protein DHX29 as a critical regulator of codon-dependent gene expression. Cryo-electron microscopy and selective ribosome profiling demonstrated that DHX29 directly interacts with the A-site entrance of the translating 80S ribosome, the binding site for the eEF1A•GTP•aminoacyl-tRNA ternary complex, suggesting a role in monitoring aminoacyl-tRNA sampling. Proteomic analysis further revealed that DHX29 recruits the GIGYF2•4EHP complex to mediate global suppression of nonoptimal mRNAs. These findings establish a mechanistic link between synonymous codon usage and the regulation of gene expression.