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bioRxiv · 10.1101/2021.08.16.456581

Specific length and structure rather than high thermodynamic stability enable regulatory mRNA stem-loops to pause translation

Bao, C.·Zhu, M.·Nykonchuk, I.·Wakabayashi, H.·Mathews, D.·Ermolenko, D.
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Abstract

Translating ribosomes unwind mRNA secondary structures by three basepairs each elongation cycle. Despite the ribosome helicase, certain mRNA stem-loops stimulate programmed ribosomal frameshift by inhibiting translation elongation. Here, using mutagenesis, biochemical and single-molecule experiments, we examine whether high stability of three basepairs, which are unwound by the translating ribosome, is critical for inducing ribosome pauses. We find that encountering frameshift-inducing mRNA stem-loops from the E. coli dnaX mRNA and the gag-pol transcript of Human Immunodeficiency Virus (HIV) hinders A-site tRNA binding and slows down ribosome translocation by 15-20 folds. By contrast, unwinding of first three basepairs adjacent to the mRNA entry channel slows down the translating ribosome by only 2-3 folds. Rather than high thermodynamic stability, specific length and structure enable regulatory mRNA stem-loops to stall translation by forming inhibitory interactions with the ribosome. Our data provide the basis for rationalizing transcriptome-wide studies of translation and searching for novel regulatory mRNA stem-loops.

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Bao, C., Zhu, M., Nykonchuk, I., Wakabayashi, H., Mathews, D., Ermolenko, D.. 2021-08-17. Specific length and structure rather than high thermodynamic stability enable regulatory mRNA stem-loops to pause translation. https://doi.org/10.1101/2021.08.16.456581

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