TARGETING OF DNA-POLYMERASE TO THE ADENOVIRUS ORIGIN OF DNA-REPLICATION BY INTERACTION WITH NUCLEAR FACTOR-I

Efficient initiation by the DNA polymerase of adenovirus type 2 requir es nuclear factor I(NFI), a cellular sequence-specific transcription f actor. Three functions of NFI-dimerization, DNA binding, and activatio n of DNA replication-are colocalized within the N-terminal portion of the protein. To define more precisely the role of NFI in viral DNA rep lication, a series of site directed mutations within the N-terminal do main have been generated, thus allowing the separation of all three fu nctions contained within this region. Impairment of the dimerization f unction prevents sequence-specific DNA binding and in turn abolishes t he NFI-mediated activation of DNA replication. NFI DNA-binding activit y, although necessary, is not sufficient to activate the initiation of adenovirus replication. A distinct class of NFI mutations that abolis h the recruitment of the viral DNA polymerase to the origin also preve nt the activation of replication. Thus, a direct interaction of NFI wi th the viral DNA polymerase complex is required to form a stable and a ctive preinitiation complex on the origin and is responsible for the a ctivation of replication by NFI.