This study presents a comprehensive analysis of mRNA and protein levels and turnover in mammalian cells using parallel metabolic pulse labeling. The researchers measured the abundance and turnover of over 5,000 genes by combining mass spectrometry and next-generation sequencing. They found that mRNA and protein levels correlated better than previously thought, but their half-lives showed no correlation. A quantitative model was used to predict synthesis rates of mRNAs and proteins, revealing that protein abundance is predominantly controlled at the translation level. Genes with similar combinations of mRNA and protein stabilities shared functional properties, suggesting that half-lives evolved under energetic and dynamic constraints. The study provides a rich resource for understanding the design principles of gene expression and offers insights into the regulation of gene expression at different levels.This study presents a comprehensive analysis of mRNA and protein levels and turnover in mammalian cells using parallel metabolic pulse labeling. The researchers measured the abundance and turnover of over 5,000 genes by combining mass spectrometry and next-generation sequencing. They found that mRNA and protein levels correlated better than previously thought, but their half-lives showed no correlation. A quantitative model was used to predict synthesis rates of mRNAs and proteins, revealing that protein abundance is predominantly controlled at the translation level. Genes with similar combinations of mRNA and protein stabilities shared functional properties, suggesting that half-lives evolved under energetic and dynamic constraints. The study provides a rich resource for understanding the design principles of gene expression and offers insights into the regulation of gene expression at different levels.