Post-transcriptional m ⁶A editing of HIV-1 mRNAs enhances viral gene expression

Summary

Covalent addition of a methyl group to the adenosine N ⁶ (m ⁶A) is an evolutionarily conserved and common RNA modification that is thought to modulate several aspects of RNA metabolism. While the presence of multiple m ⁶A editing sites on diverse viral RNAs was reported starting almost 40 years ago, how m ⁶A editing affects virus replication has remained unclear. Here, we used photo-crosslinking-assisted m ⁶A sequencing techniques to precisely map several m ⁶A editing sites on the HIV-1 genome and report that they cluster in the HIV-1 3’ untranslated region (3'UTR). Viral 3'UTR m ⁶A sites or analogous cellular m ⁶A sites strongly enhanced mRNA expression in cis by recruiting the cellular YTHDF m ⁶A “reader” proteins. Reducing YTHDF expression inhibited, while YTHDF overexpression enhanced, HIV-1 protein and RNA expression, and virus replication in CD4+ T cells. These data identify m ⁶A editing, and the resultant recruitment of YTHDF proteins, as major positive regulators of HIV-1 mRNA expression.