Codon-specific ribosome stalling reshapes translational dynamics during branched-chain amino acid starvation

This study investigates the immediate effects of single, double, and triple branched-chain amino acid (BCAA) deprivation on translational dynamics in NIH3T3 cells. Using a multi-omics approach combining RNA-seq, ribosome profiling (Ribo-seq), quantitative proteomics, and tRNA charging assays, we systematically assessed global translational output and codon-specific ribosome dwell times. Our findings reveal that BCAA starvation induces diverse and non-additive translational control patterns, reflecting a complex interplay between mTORC1 and GCN2 pathway activation, tRNA isoacceptor availability, and transcript codon usage. Notably, we identified a positional effect where the enrichment of valine codons at the 5' end of transcripts creates an elongation bottleneck under valine and triple BCAA starvation, impacting downstream ribosome occupancy and overall protein output. This study uncovers a previously underappreciated layer of complexity in BCAA-specific translational regulation.