Fig. 8. Model of the influenza virus cap-snatching mechanism, in which the processes of RNA activation of the polymerase, endonuclease cleavage of capped CA-containing RNA substrates and initiation of mRNA synthesis are coupled. Base-pairing between 5′ and 3′ vRNA: solid lines denote base-pairs required for initiation; dotted lines indicate base-pairs that enhance initiation. Dotted lines are also shown for the postulated base-pairing (i) between the 3′ terminal A of the capped RNA fragment and the 3′ terminal U of 3′ vRNA and (ii) between the initiating GTP and the 3′ penultimate C of 3′ vRNA.