Codon Usage and Amino Acid Identity Are Major Determinants of MRNA Stability in Humans

mRNA degradation is a critical, yet poorly understood, aspect of gene expression. Previ-ous studies demonstrate that codon content acts as a major determinant of mRNA stabil-ity in model organisms. In humans, the importance of open reading frame (ORF)-mediated regulation remains unclear. Here, we globally analyzed mRNA stability for both endogenous and human ORFeome collection mRNAs in human cells. Consistent with previous studies, we observed that synonymous codon usage impacts human mRNA decay. Unexpectedly, amino acid identity also acts as a driver of translation-dependent decay, meaning that primary protein sequence dictates overall mRNA levels and, conse-quently, protein abundance. Both codon usage and amino acid identity affect translational elongation rate to varying degrees in distinct organisms, with the net result being sensed by mRNA degradation machinery. In humans, interplay between ORF- and UTR-mediated control of mRNA stability may be critical to offset this fundamental relationship between protein sequence and mRNA abundance..