RNA Ribosylation's Role in Viral RNA Biology and Innate Immunity

Post-transcriptional mRNA modifications have a major impact on viral RNA stability, translation efficiency, and sensing by the host innate immune system. Therefore, understanding how RNA modifications affect viral replication and/or host innate immune sensing is essential for understanding virus/host interactions, while providing new insights into both the regulation of specific types of RNA modifications and their functional importance that are more broadly relevant to understanding RNA biology. ADP-ribosylation (ADPr) is an important post-translational modification of proteins, and several mammalian poly ADP-ribose polymerases (PARPs) are interferon stimulated genes (ISGs) that exert potent antiviral activity by placing mono-ADP-ribose (MAR) or poly- ADP-ribose (PAR) on essential viral proteins. While the effect of ADPr modification of proteins is well characterized, recent studies have found that several PARPs can ribosylate RNA in vitro and in cells, and cellular stress induces RNA ribosylation in mammalian cells. RNA ribosylation increases RNA stability but inhibits mRNA translation. In preliminary studies, we find that infection with chikungunya virus (CHIKV), an emerging alphavirus that causes severe debilitating arthritis in infected humans, results in increased levels of RNA ribosylation of both viral and host RNAs. We also demonstrate that a CHIKV mutant with diminished macrodomain-mediated ribosylhydrolase activity led to increased RNA ribosylation, and ribosylated viral RNA is translated less efficiently both within the cell and in cell free translation systems. Further analysis found that ribosylated RNA is less stable and induces a more robust antiviral response than unmodified RNA, and these effects are dependent upon expression of the host Zinc Finger Antiviral Protein (ZAP). Therefore, as part of this highly innovative R21 application we propose to further investigate the impact of RNA ribosylation on viral RNA translation efficiency, while also investigating ZAP’s role in sensing ribosylated RNAs to inhibit viral replication and initiate antiviral immune responses within the infected cell. These studies, which take advantage of our collaborative team’s expertise in RNA biology, translational control, molecular virology, and innate immunity will provide important new insights into a novel role for ribosylation in regulating viral RNA biology and innate immune control of viral infections. Project Number: 1R21AI196787-01 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Mark Heise (+1 co-PI) | Institution: UNIV OF NORTH CAROLINA CHAPEL HILL, CHAPEL HILL, NC | Award Amount: $229,714 | Activity Code: R21 | Study Section: Viral Pathogenesis and Immunity Study Section [VPI] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R21AI19678701