Methyltransferase Like 3 and Fat Mass and Obesity-Associated Protein Are Required for H7N9 Infection in Cell Culture

Background METTL3 (methyltransferase like 3) and FTO (fat mass and obesity-associated protein) are criticalfor establishing and regulating the m6A (N6-methyladenosine) modification, but very little is known about thefunction of m6A in the immune system or its role in interactions within the host immune system.Methods Western blotting experiment was used to check the expression of the host proteins related to m6Amodification after H7N9 influenza virus infection. Immunofluorescence experiment was used to identifywhether the subcellular localization of related proteins. Moreover, we knocked down and over expressendogenous METTL3 or FTO in A549 cells, and then infected the cells with H7N9 to test whethermethyltransferases or demethylases affect H7N9 replication.Result We confirmed that the expression pattern of m6A proteins was altered during H7N9 infection. METTL3and FTO were located in the nucleus, and YTHDF3 was located in the cytoplasm. Furthermore, our resultsdemonstrate that downregulation of METTL3 or FTO expression in A549 cells severely impairs viral proteinexpression and H7N9 infection.Conclusions METTL3 and FTO are critical for H7N9 replication which may represent a new mechanism for thecontrol of H7N9 replication and host-pathogen interactions.