Boric acid intercepts 80S ribosome migration from AUG-stop by stabilizing eRF1 at the A site

In response to environmental changes, cells flexibly and rapidly alter gene expression, through translational controls. In plants, the translation of NIP5;1, a boric acid diffusion facilitator, is upregulated through upstream open reading frames (uORFs) that comprise only AUG and stop codons, in response to a shortage of boric acid in the environment. However, the molecular details of how the minimum uORF controls the translation of the downstream main ORF, in a boric acid concentration-dependent manner, have remained unclear. Here, combining ribosome profiling, TCP-Seq, structural analysis with cryo-electron microscopy, and biochemical assays, we showed that the 80S ribosome (80S) assembled at AUG-stop migrates into the subsequent RNA segment, followed by downstream translation initiation, and that boric acid impedes this process by the stable confinement of eukaryotic release factor 1 (eRF1) on the 80S on AUG-stop. Our results provide molecular insight into translation regulation by a minimum and environment-responsive uORF. Overall design: Translation complex profile sequencing (TCP-seq)