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bioRxiv · 10.64898/2026.04.23.720132

Ribosome collisions trigger tmRNA-mediated rescue through mRNA disengagement

Metelev, M.·Borg, A.·Akbar, S.·Larsson, D. S. D.·Seefeldt, A. C.·Selmer, M.·Johansson, M.
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Abstract

Ribosome rescue pathways maintain translation during normal growth and contribute to stress tolerance. In Escherichia coli, HrpA is a ribosome-collision recognition factor that mediates antibiotic tolerance by resolving stalled ribosomes, yet the fate of the resulting ribosomal intermediate, with a topologically trapped peptidyl-tRNA in the 50S nascent peptide exit tunnel, has remained unclear. Using in vivo single-molecule tracking, we show that under antibiotic treatment, HrpA-dependent collision processing promotes recruitment of tmRNA and Hsp15 as downstream rescue factors. Cryo-electron microscopy of affinity-purified native complexes from tmRNA-deficient cells reveals accumulation of aberrant 70S{middle dot}peptidyl-tRNA complexes and shows that Hsp15, previously thought to interact exclusively with 50S{middle dot}peptidyl-tRNA, binds to 70S complexes lacking mRNA in the E site. This intermediate can be resolved by the canonical tmRNA pathway, thereby connecting HrpA-dependent collision processing to canonical tmRNA-mediated rescue.

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Metelev, M., Borg, A., Akbar, S., Larsson, D. S. D., Seefeldt, A. C., Selmer, M., Johansson, M.. 2026-04-23. Ribosome collisions trigger tmRNA-mediated rescue through mRNA disengagement. https://doi.org/10.64898/2026.04.23.720132

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