Role of tankyrase in host antiviral responses to influenza virus infection

Influenza viruses are significant respiratory pathogens that infect many species and can cause seasonal epidemics and unpredictable pandemics in humans. The emergence of resistance to approved anti-influenza drugs that target viral proteins warrants the research to identify host factors essential for virus replication. This will provide new targets for developing next-generation anti-influenza drugs. Cellular poly(ADP-ribose) polymerases, Tankyrase 1 and 2 (TNKS1 and TNKS2) are involved in many biological processes. We found that TNKS1/2 expression was elevated in human primary bronchial/tracheal epithelial cell, human epithelial (A549 and HEK293) cell lines and mouse lungs during influenza A virus (IAV) infection. Knock-down of TNKS1/2 by RNA interference (RNAi) reduced viral replication. Using a computation approach, 3’-untranslation regions (3’-UTR) reporter assay, and measuring endogenous protein expression, we identified miR-9-1 and miR-206 as the microRNAs that targeted TNKS1 and TNKS2, respectively. Ectopic expression of both microRNAs reduced IAV replication as determined by viral mRNA and protein levels as well as virus production in cell culture. Importantly, overexpression of miR-206 or miR-9-1 activated JAK/Stat signaling and induced type I interferons (IFNs) responses against IAV infection. The delivery of an adenovirus expressing miR-9-1 or miR-206 into the lung of mice suppressed TNKS1 and TNKS2, respectively. When these mice were challenged with IAV, they induced type I IFN responses, suppressed viral load in the lungs, and increased survival. Targeting host factors via microRNAs have some limitations including off-target effects. To address this, we used TNKS1/2 single and double knockout (TNKS1 KO, TNKS2 KO, and DKO) HEK293T cells to evaluate their effects on IAV infection. TNKS KOs significantly attenuated IAV replication and the largest effect was observed in DKO cells. Moreover, DKO cells had enhanced type I IFN responses. Finally, TNKS1 and TNKS2 KO mice challenged with IAV showed increased type I IFN responses, decreased viral load in the lungs, and increased survival from a lethal IAV infection. In conclusion, TNKS inhibition repressed IAV replication by activating the antiviral state and our findings may expand the knowledge of developing anti-influenza therapeutics.