Abstract
The ribosome mRNA channel is central to translation, yet its role in regulatory mechanisms remains unclear. Using cryo-EM of human ribosomal complexes bound to Kozak and TISU mRNAs from wild-type (WT) and RPS26/eS26 mutant (RPS26dC) cells, we demonstrate that both RPS26/eS26 and mRNA adopt distinct conformations, explaining the opposing effects of RPS26dC on their activity. Translatome studies of WT and RPS26dC reveal AUG-context-dependent changes in 48S and 80S initiation complexes and slower scanning. Downregulated mRNAs are enriched for specific AUG-upstream nucleotides and a −1-cytosine contacting 18S rRNA G1207, an interaction lost in RPS26dC. Strongly affected transcripts include replication-dependent histones, which, despite short 5′UTRs and suboptimal Kozak, exhibit robust translation activity that is RPS26/eS26-dependent. We identify a translational enhancer in the H2B 5′UTR (−16 to −9) overlapping predicted RPS26/eS26-binding sites, with a distinct ribosome-bound conformation. Exploiting these features, we engineered a high-efficiency translational cassette with minimal leaky scanning. These findings underscore the role of the ribosome’s mRNA channel in selective translation and its therapeutic potential.
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Acknowledgements
We thank the G-INCPM deep sequencing team of the Weizmann Institute for the RNA-seq. This work was supported by the Israel Science Foundation (#1199/22), the Kimmelman Center for Macromolecular Assemblies, and by Weizmann Institute internal grants from the Estate of Manfred and Margaret Tannen and Joel and Mady Dukler Fund for Cancer Research. R.D. is the incumbent of the Ruth and Leonard Simon Chair of Cancer Research.
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Fraticelli, D., Hiregange, D.G., Weiss, B. et al. Structural and molecular basis of specialized translation mediated by the ribosome mRNA-binding channel. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72263-5
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DOI: https://doi.org/10.1038/s41467-026-72263-5
