LAUSR

In pathophysiology, reactive oxygen species oxidize biomolecules that contribute to disease phenotypes 1 . One such modification, 8-oxoguanine 2 (o 8 G), is abundant in RNA 3 but its epitranscriptional role has not been investigated for microRNAs (miRNAs). Here we specifically sequence oxidized miRNAs in a rat model of the redox-associated condition cardiac hypertrophy 4 . We find that position-specific o 8 G modifications are generated in seed regions (positions 2–8) of selective miRNAs, and function to regulate other mRNAs through o 8 G•A base pairing. o 8 G is induced predominantly at position 7 of miR-1 (7o 8 G-miR-1) by treatment with an adrenergic agonist. Introducing 7o 8 G-miR-1 or 7U-miR-1 (in which G at position 7 is substituted with U) alone is sufficient to cause cardiac hypertrophy in mice, and the mRNA targets of o 8 G-miR-1 function in affected phenotypes; the specific inhibition of 7o 8 G-miR-1 in mouse cardiomyocytes was found to attenuate cardiac hypertrophy. o 8 G-miR-1 is also implicated in patients with cardiomyopathy. Our findings show that the position-specific oxidation of miRNAs could serve as an epitranscriptional mechanism to coordinate pathophysiological redox-mediated gene expression. The 8-oxoguanine modification of the microRNA miR-1 results in redirected recognition and silencing of target genes and leads to cardiac hypertrophy in mice.