Insights into the base-pairing preferences of 8-oxoguanosine on the ribosome

Abstract Of the four bases, guanine is the most susceptible to oxidation, which results in the formation of 8-oxoguanine (8-oxoG). In protein-free DNA, 8-oxodG adopts the syn conformation more frequently than the anti one. In the syn conformation, 8-oxodG base pairs with dA. The equilibrium between...

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Veröffentlicht in:Nucleic acids research 2019-10, Vol.47 (18), p.9857-9870
Hauptverfasser: Thomas, Erica N, Simms, Carrie L, Keedy, Hannah E, Zaher, Hani S
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Sprache:eng
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Zusammenfassung:Abstract Of the four bases, guanine is the most susceptible to oxidation, which results in the formation of 8-oxoguanine (8-oxoG). In protein-free DNA, 8-oxodG adopts the syn conformation more frequently than the anti one. In the syn conformation, 8-oxodG base pairs with dA. The equilibrium between the anti and syn conformations of the adduct are known to be altered by the enzyme recognizing 8-oxodG. We previously showed that 8-oxoG in mRNA severely disrupts tRNA selection, but the underlying mechanism for these effects was not addressed. Here, we use miscoding antibiotics and ribosome mutants to probe how 8-oxoG interacts with the tRNA anticodon in the decoding center. Addition of antibiotics and introduction of error-inducing mutations partially suppressed the effects of 8-oxoG. Under these conditions, rates and/or endpoints of peptide-bond formation for the cognate (8-oxoG•C) and near-cognate (8-oxoG•A) aminoacyl-tRNAs increased. In contrast, the antibiotics had little effect on other mismatches, suggesting that the lesion restricts the nucleotide from forming other interactions. Our findings suggest that 8-oxoG predominantly adopts the syn conformation in the A site. However, its ability to base pair with adenosine in this conformation is not sufficient to promote the necessary structural changes for tRNA selection to proceed.
ISSN:0305-1048
1362-4962
DOI:10.1093/nar/gkz701