title: Methionine-101 from one strain of H5N1 NS1 protein determines its IFN-antagonizing ability and subcellular distribution pattern.
abstract: Influenza A virus NS1 protein has developed two main IFN-antagonizing mechanisms by inhibiting retinoic-acid-inducible gene I (RIG-I) signal transduction, or by suppressing cellular pre-mRNA processing through binding to cleavage and polyadenylation specific factor 30 (CPSF30). However, the precise effects of NS1 on suppressing type I IFN induction have not been well characterized. Here we report that compared with PR/8/34 NS1, which is localized partially in the cytoplasm and has strong IFN-antagonizing ability via specifically inhibiting IFN-β promoter activity, H5N1 NS1 has strikingly different characteristics. It mainly accumulates in the nucleus of transfected cells and exerts rather weak IFN-counteracting ability through suppression of the overall gene expression. The M101I mutation of H5N1 NS1, namely H5-M101I, fully reversed its functions. H5-M101I gained the ability to specifically inhibit IFN-β promoter activity, translocate to the cytoplasm, and release CPSF30. The previously reported NES (nuclear export signal) (residues 138-147) was unable to lead H5N1 NS1 to translocate. This suggests that other residues may serve as a potent NES. Findings indicated that together with leucine-100, methionine-101 enhanced the regional NES. In addition, methionine-101 was the key residue for the NS1-CPSF30 interaction. This study reveals the importance of methionine-101 in the influenza A virus life cycle and may provide valuable information for antiviral strategies.
authors.affiliation: State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Meng
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Zheng
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Hanzhong
authors.initials: H
authors.lastname: Wang
mesh_terms: D015153:Blotting, Western; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000737:chemistry*; D007372:Interferons / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008715:Methionine / Q000032:analysis*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009154:Mutation; D011401:Promoter Regions, Genetic; D013347:Subcellular Fractions / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: C085820:INS1 protein, influenza virus; D017361:Viral Nonstructural Proteins; D007372:Interferons; D008715:Methionine