title: Effect of reassortment on the nucleotide and amino acid changes of human A/H3N2 RNP subunits during 1998-2009.
abstract: BACKGROUND
  The ribonucleoprotein (RNP) complex of influenza virus consists of four subunits PB2, PB1, PA, and NP, which are essential for replication. While reassortment plays an important role in the evolution and virulence of influenza viruses, limited studies have investigated the effect of reassortment on the evolution of the internal RNP subunits.
  
  
  OBJECTIVE
  To examine the effect of reassortment on the nucleotide and amino acid changes of human A/H3N2 RNP subunits during the period 1998-2009.
  
  
  METHODS
  A total of 240 A/H3N2 RNP subunit sequences were obtained from 23 clinical isolates in Australia and 217 isolates from National Centre for Biotechnology Information (NCBI) database. Rates of nucleotide change, amino acid substitution profile and phylogenetic analysis of each subunit during the 12-year period were determined using MEGA5.
  
  
  RESULTS
  A major reassortment event within the A/H3N2 RNP subunits occurred in 2003. The rates of nucleotide change for PB2, PB1 and PA differed significantly before and after 2003, and were low compared to surface protein haemagglutinin (HA). No change was observed for NP. The amino acid substitution profile of the RNP subunits during the 12-year period showed the presence of simultaneous amino acid fixations in a pattern similar to HA, with an average amino acid fixation rate of 1.57 years.
  
  
  CONCLUSIONS
  Reassortment can affect the evolution of the influenza RNP subunits. Monitoring the amino acid substitution profile and evolution of the RNP subunits is necessary for the surveillance of future reassortments and emergence of potential virulence markers in the population.
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney 2052, Australia.
authors.forename: Karen Ka Yin
authors.initials: KK
authors.lastname: Wong
authors.forename: Rowena A
authors.initials: RA
authors.lastname: Bull
authors.forename: Sacha
authors.initials: S
authors.lastname: Stelzer-Braid
authors.forename: Michael
authors.initials: M
authors.lastname: Fennell
authors.forename: William
authors.initials: W
authors.lastname: Rawlinson
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D001315:Australia; D016000:Cluster Analysis; D019143:Evolution, Molecular; D005838:Genotype; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000821:virology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017354:Point Mutation; D021122:Protein Subunits / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D016865:Reassortant Viruses / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D021122:Protein Subunits; D012367:RNA, Viral; D014764:Viral Proteins