Felix Naef

eLife Assessment This important study provides evidence for dynamic coupling between translation initiation and elongation that can help maintain low ribosome density and translational homeostasis. The authors combine single-molecule imaging with a new approach to analyze mRNA translation kinetics using Bayesian modeling. This work is overall solid and will be of interest to those studying translational regulation.

NIH3T3 mouse fibroblast cells were cultured in DMEM (high glucose, pyruvate; Gibco) supplemented with 10% FBS (qualified, USDA-approved regions; Gibco), and 100 U/ml penicillin–streptomycin (Gibco). Cells were maintained at 37 °C in a humidified incubator with 5% CO₂.

Abstract mRNA translation involves multiple regulatory steps, but how translation elongation influences protein output remains unclear. Using SunTag live-cell imaging and mathematical modeling, we quantified translation dynamics in single mRNAs across diverse coding sequences. Our Totally Asymmetric Exclusion Process (TASEP)-based model revealed a strong coordination between initiation and elongation rates, resulting in consistently low ribosome density (<12% occupancy) across all reporters.