Reverse Transcription Past Products of Guanine Oxidation in RNA Leads to Insertion of A and C opposite 8-Oxo-7,8-dihydroguanine and A and G opposite 5-Guanidinohydantoin and Spiroiminodihydantoin Diastereomers.

Abstract

Reactive oxygen species, both endogenous and exogenous, can damage nucleobases of RNA and DNA. Among the nucleobases, guanine has the lowest redox potential, making it a major target of oxidation. Although RNA is more prone to oxidation than DNA is, oxidation of guanine in RNA has been studied to a significantly lesser extent. One of the reasons for this is that many tools that were previously developed to study oxidation of DNA cannot be used on RNA. In the study presented here, the lack of a method for seeking sites of modification in RNA where oxidation occurs is addressed. For this purpose, reverse transcription of RNA containing major products of guanine oxidation was used. Extension of a DNA primer annealed to an RNA template containing 8-oxo-7,8-dihydroguanine (OG), 5-guanidinohydantoin (Gh), or the R and S diastereomers of spiroiminodihydantoin (Sp) was studied under standing start conditions. SuperScript III reverse transcriptase is capable of bypassing these lesions in RNA inserting predominantly A opposite OG, predominantly G opposite Gh, and almost an equal mixture of A and G opposite the Sp diastereomers. These data should allow RNA sequencing of guanine oxidation products by following characteristic mutation signatures formed by the reverse transcriptase during primer elongation past G oxidation sites in the template RNA strand.