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J Biol Chem. 2013 Feb 22. [Epub ahead of print]
Structural and Functional Characterization of K339T Substitution Identified in the PB2 Cap-binding Pocket of Influenza A Virus.
Liu Y, Qin K, Meng G, Zhang J, Zhou J, Zhao G, Luo M, Zheng X.
Source
Peking University, China;
Abstract
Influenza virus RNA-dependent RNA polymerase (RdRp) is a heterotrimer composed of PA, PB1 and PB2 subunits. RdRp is required for both transcription and replication of influenza viral RNA taking place in the nucleus of infected cells. A 'cap-snatching' mechanism is employed to generate a 5'-capped primer for transcription, in which the cap-binding domain of PB2 (PB2cap) captures the 5' cap of the host pre-mRNA. Our statistical analysis of PB2 sequences showed that residue Lys339 located in the cap-binding pocket of H5N1 PB2cap was gradually replaced by Thr339 over the past decade. To understand the role of this amino acid polymorphism, we solved the crystal structures of PB2cap with or without a pre-mRNA cap analog m7GTP in the presence of Lys339 or Thr339. The structures showed that Lys339 contributes to binding the γ-phosphate group of m7GTP, and the replacement of Lys339 by Thr eliminates this interaction. Isothermal titration calorimetry analysis showed that Thr339 attenuated the PB2cap cap-binding activity in vitro compared to Lys339. Further functional studies confirmed that Thr339-PB2-containing RNP has a reduced influenza polymerase activity and RNA synthesis activity, and a reconstituted H5N1 virus containing the Thr339 substitution exhibited a lower virulence to mice while more active replication in MDCK cells. The K339T substitution in the cap-binding pocket of PB2 modulates the polymerase activity and virulence by regulating the cap-binding activity. It is informative to track variations in the cap-binding pocket of PB2 in surveillance of the evolution and spread of influenza virus.
PMID:
23436652
[PubMed - as supplied by publisher]
Free full text
Structural and Functional Characterization of K339T Substitution Identified in the PB2 Cap-binding Pocket of Influenza A Virus.
Liu Y, Qin K, Meng G, Zhang J, Zhou J, Zhao G, Luo M, Zheng X.
Source
Peking University, China;
Abstract
Influenza virus RNA-dependent RNA polymerase (RdRp) is a heterotrimer composed of PA, PB1 and PB2 subunits. RdRp is required for both transcription and replication of influenza viral RNA taking place in the nucleus of infected cells. A 'cap-snatching' mechanism is employed to generate a 5'-capped primer for transcription, in which the cap-binding domain of PB2 (PB2cap) captures the 5' cap of the host pre-mRNA. Our statistical analysis of PB2 sequences showed that residue Lys339 located in the cap-binding pocket of H5N1 PB2cap was gradually replaced by Thr339 over the past decade. To understand the role of this amino acid polymorphism, we solved the crystal structures of PB2cap with or without a pre-mRNA cap analog m7GTP in the presence of Lys339 or Thr339. The structures showed that Lys339 contributes to binding the γ-phosphate group of m7GTP, and the replacement of Lys339 by Thr eliminates this interaction. Isothermal titration calorimetry analysis showed that Thr339 attenuated the PB2cap cap-binding activity in vitro compared to Lys339. Further functional studies confirmed that Thr339-PB2-containing RNP has a reduced influenza polymerase activity and RNA synthesis activity, and a reconstituted H5N1 virus containing the Thr339 substitution exhibited a lower virulence to mice while more active replication in MDCK cells. The K339T substitution in the cap-binding pocket of PB2 modulates the polymerase activity and virulence by regulating the cap-binding activity. It is informative to track variations in the cap-binding pocket of PB2 in surveillance of the evolution and spread of influenza virus.
PMID:
23436652
[PubMed - as supplied by publisher]
Free full text
