The N-terminal extension of the influenza B virus nucleoprotein is not required for nuclear accumulation or the expression and replication of a model RNA.
The nucleoprotein (NP) of influenza B virus is 50 amino acids longer at the N-terminus than influenza A virus NP and lacks homology to the A virus protein over the first 69 residues. We have deleted the N-terminal 51 and 69 residues of the influenza B/Ann Arbor/1/66 virus NP and show that nuclear accumulation of the protein is unaffected. This indicates that the nuclear localization signal is not located at the extreme N terminus, as in influenza A virus NP. To determine if the N-terminal mutants could support the expression and replication of a model influenza B virus RNA, the genes encoding the subunits of the viral RNA-dependent RNA polymerase (PA, PB1, and PB2) were cloned. Coexpression of NP and the P proteins in 293 cells was found to permit the expression and replication of a transfected model RNA based on segment 4 of B/Maryland/59, in which the hemagglutinin-coding region was replaced by a chloramphenicol acetyltransferase gene. The expression and replication of the synthetic RNA were not affected by the replacement of NP with NP mutants lacking the N-terminal 51 or 69 residues, indicating that the N-terminal extension is not required for transcription or replication of the viral RNA. In addition, we report that the influenza B virus NP cannot be functionally replaced by type A virus NP in this system.
Stevens
M P
MP
School of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ, United Kingdom.
Barclay
W S
WS
D000595:Amino Acid Sequence; D002460:Cell Line; D005814:Genes, Viral; D006801:Humans; D009981:Influenza B virus / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D009698:Nucleoproteins / Q000737:chemistry / Q000502:physiology; D012367:RNA, Viral / Q000235:genetics*; D016415:Sequence Alignment; D017384:Sequence Deletion; D014758:Viral Core Proteins / Q000737:chemistry / Q000502:physiology*; D014779:Virus Replication
D009698:Nucleoproteins; D012367:RNA, Viral; D014758:Viral Core Proteins