J Virol. 2019 Jan 16. pii: JVI.01587-18. doi: 10.1128/JVI.01587-18. [Epub ahead of print]
Epigenetic modification is regulated by the interaction of influenza A virus nonstructural protein-1 with the de novo DNA methyltransferase DNMT3B and subsequent transport to the cytoplasm for K48-linked polyubiquitination.

Liu S1, Liu L1, Xu G1, Cao Z1, Wang Q1, Li S1, Peng N1, Yin J1, Yu H1, Li M1, Xia Z1, Zhou L2, Lin Y3, Wang X3, Li Q3, Zhu C4, Yang X5, Wang J6, She Y1, Lu M3, Zhu Y7.
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The influenza virus NS1 protein is a non-structural protein that plays a major role in antagonizing host interferon responses during infection. However, a clear role for NS1 in epigenetic modification has not been established. In this study, NS1 regulates the expression of some key regulators of JAK-STAT signaling by inhibiting the DNA methylation of their promoters. Furthermore, DNA methyltransferase 3B (DNMT3B) is responsible for this process. Upon investigating the mechanisms underlying this event, NS1 interacts with DNMT3B, but not DNMT3A, leading to the dissociation of DNMT3B from the promoters of the corresponding genes. In addition, the interaction between NS1 and DNMT3B changes the localization of DNMT3B from the nucleus to the cytosol, resulting in K48-linked ubiquitination and degradation of DNMT3B in the cytosol. Conclusion: NS1 interacts with DNMT3B and changes its localization to mediate K48-linked polyubiquitination, subsequently contributing to the modulation of the expression of JAK-STAT signaling suppressors.Importance The NS1 protein of influenza A virus (IAV) is a multifunctional protein that counters cellular antiviral activities and is a virulence factor. However, the involvement of NS1 protein in DNA methylation during IAV infection has not been established. Here, we reveal that the NS1 protein binds the cellular DNMT3B DNA methyltransferase, thereby inhibiting the methylation of the promoters of genes encoding suppressors of JAK-STAT signaling. As a result, these suppressor genes are induced, and JAK-STAT signaling is inhibited. Further, we demonstrate that the NS1 protein transports DNMT3B to the cytoplasm for ubiquitination and degradation. Thus, we identify the NS1 protein as a potential trigger of the epigenetic deregulation of JAK-STAT signaling suppressors and illustrate a novel mechanism underlying the regulation of host immunity during IAV infection.
Copyright 2019 American Society for Microbiology.

PMID: 30651365 DOI: 10.1128/JVI.01587-18