Acetylation of cytidine residues boosts HIV-1 gene expression by increasing viral RNA stability

Covalent modifications added to individual nucleotides on mRNAs, called epitranscriptomic modifications, have recently emerged as key regulators of both cellular and viral mRNA function and RNA methylation has now been shown to enhance the replication of human immunodeficiency virus 1 (HIV-1) and several other viruses. Recently, acetylation of the N4 position of cytidine (ac4C) was reported to boost cellular mRNA function by increasing mRNA translation and stability. We therefore hypothesized that ac4C and N-acetyltransferase 10 (NAT10), the cellular enzyme that adds ac4C to RNAs, might also have been subverted by HIV-1 to increase viral gene expression. We now confirm that HIV-1 transcripts are indeed modified by addition of ac4C at multiple discreet sites and demonstrate that silent mutagenesis of a subset of these ac4C addition sites inhibits HIV-1 gene expression in cis. Moreover, reduced expression of NAT10, and the concomitant decrease in the level of ac4C on viral RNAs, inhibits HIV-1 replication by reducing HIV-1 RNA stability. Interestingly Remodelin, a previously reported inhibitor of NAT10 function, also inhibits HIV-1 replication without affecting cell viability, thus raising the possibility that the addition of ac4C to viral mRNAs might emerge as a novel cellular target for antiviral drug development.