Characterisation of the adenovirus preterminal protein and its interactionwith the POU homeodomain of NFIII (Oct-1)

Formation of the preinitiation complex for adenovirus DNA replication invol ves the incoming preterminal protein-adenovirus DNA polymerase heterodimer being positioned at the origin of replication by protein-DNA and protein-pr otein interactions, Preterminal protein directly binds to the cellular tran scription factor nuclear factor III (Oct-1), via the POU homeodomain. Co-pr ecipitation of POU with individual domains of preterminal protein expressed by in vitro translation indicated that POU contacts multiple sites on pret erminal protein. Partial proteolysis of preterminal protein in the presence or absence of POU homeodomain demonstrated that many sites accessible to p roteases in free preterminal protein were resistant to cleavage in the pres ence of POU homeodomain. The accessibility of sites in free preterminal pro tein to cleavage by trypsin was strongly dependent on the ionic strength, s uggesting that preterminal protein may undergo a sodium chloride-induced co nformational change. It is therefore likely that the POU homeodomain contac ts a number of sites on preterminal protein to induce a conformational chan ge which may influence the initiation of adenovirus DNA replication.