THE ROLE OF TEMPLATE-PRIMER INTERACTIONS IN CLEAVAGE AND INITIATION BY THE INFLUENZA-VIRUS POLYMERASE

An in vitro cleavage/initiation assay was used to analyse cleavage sit e choice and transcription initiation by the influenza virus polymeras e. A synthetic mRNA which is cleaved by the polymerase to produce a si ngle 11 base primer fragment was altered around this cleavage site. De pending upon the mutations made, alternative cleavage sites were used. This system was then used in extracts from recombinant vaccinia virus infected cells which express the polymerase. These extracts require t he addition of a synthetic vRNA in order to induce cleavage and initia tion activity. The data show that the choice of cleavage site is whole ly controlled by the mRNA and does not depend upon interactions with t he vRNA template. However, the site of initiation of the cleaved prime r on the template is influenced by template-primer interactions.