Association of the Influenza Virus RNA Polymerase Subunit PB2 with the Host Chaperonin CCT {triangledown}

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Association of the Influenza Virus RNA Polymerase Subunit PB2 with the Host Chaperonin CCT <sup>

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http://jvi.asm.org/cgi/content/abstract/84/17/8691


Tatiana Fislov?,¹^,2 Benjamin Thomas,³ Katy M. Graef,¹^,4<sup>,

</sup> and Ervin Fodor¹^* Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom,¹ Institute of Virology, Slovak Academy of Sciences, Bratislava, Slovak Republic,² Oxford Central Proteomics Facility, Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom,³ Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892⁴
Received 16 April 2010/ Accepted 14 June 2010
<!-- ABS --> The RNA polymerase of influenza A virus is a host range determinantand virulence factor. In particular, the PB2 subunit of theRNA polymerase has been implicated as a crucial factor thataffects cell tropism as well as virulence in animal models.These findings suggest that host factors associating with thePB2 protein may play an important role during viral replication.In order to identify host factors that associate with the PB2protein, we purified recombinant PB2 from transiently transfectedmammalian cells and identified copurifying host proteins bymass spectrometry. We found that the PB2 protein associateswith the cytosolic chaperonin containing TCP-1 (CCT), stress-inducedphosphoprotein 1 (STIP1), FK506 binding protein 5 (FKBP5),

-and β-tubulin, Hsp60, and mitochondrial protein p32. Someof these binding partners associate with each other, suggestingthat PB2 might interact with these proteins in multimeric complexes.More detailed analysis of the interaction of the PB2 proteinwith CCT revealed that PB2 associates with CCT as a monomerand that the CCT binding site is located in a central regionof the PB2 protein. PB2 proteins from various influenza virussubtypes and origins can associate with CCT. Silencing of CCTresulted in reduced viral replication and reduced PB2 proteinand viral RNA accumulation in a ribonucleoprotein reconstitutionassay, suggesting an important function for CCT during the influenzavirus life cycle. We propose that CCT might be acting as a chaperonefor PB2 to aid its folding and possibly its incorporation intothe trimeric RNA polymerase complex.