title: Molecular and biochemical characterization of the NS1 protein of non-cultured influenza B virus strains circulating in Singapore.
abstract: In this study we compared the NS1 protein of Influenza B/Lee/40 and several non-cultured Influenza B virus clinical strains detected in Singapore. In B/Lee/40 virus-infected cells and in cells expressing the recombinant B/Lee/40 NS1 protein a full-length 35 kDa NS1 protein and a 23 kDa NS1 protein species (p23) were detected. Mutational analysis of the NS1 gene indicated that p23 was generated by a novel cleavage event within the linker domain between an aspartic acid and proline at amino acid residues at positions 92 and 93 respectively (DP92-93), and that p23 contained the first 92 amino acids of the NS1 protein. Sequence analysis of the Singapore strains indicated the presence of either DP92-93or NP92-93in the NS1 protein, but protein expression analysis showed that p23 was only detected in NS1 proteins with DP92-93.. An additional adjacent proline residue at position 94 (P94) was present in some strains and correlated with increased p23 levels, suggesting that P94has a synergistic effect on the cleavage of the NS1 protein. The first 145 amino acids of the NS1 protein are required for inhibition of ISG15-mediated ubiquitination, and our analysis showed that Influenza B viruses circulating in Singapore with DP92-93expressed truncated NS1 proteins and may differ in their capacity to inhibit ISG15 activity. Thus, DP92-93in the NS1 protein may confer a disadvantage to Influenza B viruses circulating in the human population and interestingly the low frequency of DP92-93detection in the NS1 protein since 2004 is consistent with this suggestion.
authors.affiliation: 1​School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
authors.forename: Muhammad Raihan
authors.initials: MR
authors.lastname: Jumat
authors.affiliation: 2​Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, 117510, Singapore.
authors.forename: Puisan
authors.initials: P
authors.lastname: Wong
authors.affiliation: 3​Bioinformatics Institute (BII) 30 Biopolis Street #07-01, Matrix Building, 138671, Singapore.
authors.forename: Raphael Tze Chuen
authors.initials: RTC
authors.lastname: Lee
authors.affiliation: 1​School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.|3​Bioinformatics Institute (BII) 30 Biopolis Street #07-01, Matrix Building, 138671, Singapore.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Maurer-Stroh
authors.affiliation: 2​Detection and Diagnostics Laboratory, DSO National Laboratories, 27 Medical Drive, 117510, Singapore.
authors.forename: Boon Huan
authors.initials: BH
authors.lastname: Tan
authors.affiliation: 1​School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sugrue
mesh_terms: D006801:Humans; D009981:Influenza B virus / Q000235:genetics*; D007251:Influenza, Human / Q000821:virology*; D008297:Male; D012846:Singapore; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C085820:INS1 protein, influenza virus; D017361:Viral Nonstructural Proteins
keywords: B/Lee/40; Cleavage; Influenza B; NS1; Proteolysis