Structural study of Polymerase (PA subunit endo mutant E119D) of influenza H7N9 virus purified in high five cells

The influenza virus polymerase (FluPol) is implicated in both transcription and replication of the viral RNA (vRNA).Transcription enables the production of an mRNA which is utilised by the host cell to generate viral proteins. These viral proteins are required for virus replication and assembly of progeny virions. In order to initiate transcription FluPol must perform 'cap-snatching'. The FluPol cap-binding domain binds to a 5' capped mRNA primer and the endonuclease cleaves the cap from the rest of the mRNA strand. Our aim is to capture FluPol during 'cap-snatching' using cryo-EM. In order to achieve this we have combined a H7N9 FluPol mutant which has reduced endonuclease activity with a long capped mRNA primer, thereby stalling FluPol during the process of 'cap-snatching'.