The human H5N1 influenza A virus polymerase complex is active in vitro over a broad range of temperatures,

[Anne]

The human H5N1 influenza A virus polymerase complex is active in vitro over a broad range of temperatures, in contrast to the WSN complex, and this property can be attributed to the PB2 subunit

http://vir.sgmjournals.org/cgi/content/abstract/89/12/2923



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Birgit G. Bradel-Tretheway</nobr>, <nobr>Z. Kelley</nobr>, <nobr>Shikha Chakraborty-Sett</nobr>, <nobr>Toru Takimoto</nobr>, <nobr>Baek Kim</nobr> and <nobr>Stephen Dewhurst</nobr>
[SIZE=-1] Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA [/SIZE]

[SIZE=-1]Correspondence
Birgit Bradel-Tretheway
Birgit_BradelTretheway@urmc.rochester.edu<script type="text/javascript"><!-- var u = "Birgit_BradelTretheway", d = "urmc.rochester.edu"; document.getElementById("em0").innerHTML = '<a href="mailto:' + u + '@' + d + '">' + u + '@' + d + '<\/a>'//--></script>[/SIZE]
<!-- ABS --> Influenza A virus (IAV) replicates in the upper respiratorytract of humans at 33 °C and in the intestinal tractof birds at close to 41 °C. The viral RNA polymerasecomplex comprises three subunits (PA, PB1 and PB2) and playsan important role in host adaptation. We therefore developedan in vitro system to examine the temperature sensitivity ofIAV RNA polymerase complexes from different origins. Complexeswere prepared from human lung epithelial cells (A549) usinga novel adenoviral expression system. Affinity-purified complexeswere generated that contained either all three subunits (PA/PB1/PB2)from the A/Viet/1203/04 H5N1 virus (H/H/H) or the A/WSN/33 H1N1strain (W/W/W). We also prepared chimeric complexes in whichthe PB2 subunit was exchanged (H/H/W, W/W/H) or substitutedwith an avian PB2 from the A/chicken/Nanchang/3-120/01 H3N2strain (W/W/N). All complexes were functional in transcription,cap-binding and endonucleolytic activity. Complexes containingthe H5N1 or Nanchang PB2 protein retained transcriptional activityover a broad temperature range (30–42 °C). Incontrast, complexes containing the WSN PB2 protein lost activityat elevated temperatures (39 °C or higher). The E627Kmutation in the avian PB2 was not required for this effect.Finally, the avian PB2 subunit was shown to confer enhancedstability to the WSN 3P complex. These results show that PB2plays an important role in regulating the temperature optimumfor IAV RNA polymerase activity, possibly due to effects onthe functional stability of the 3P complex.
<!-- null --> Published online ahead of print on 11 September 2008 as DOI10.1099/vir.0.2008/006254-0.
<!-- null --> A supplementary figure is available with the online versionof this paper.

 

[gsgs]

Re: The human H5N1 influenza A virus polymerase complex is active in vitro over a broad range of temperatures,

what temperature specifity had pandemic strains ?
In the last pandemic viruses PB2 was not exchanged (but PB1 was)

so, all human flu since 1918 has the PB2 from A/Brevig/1918