REPLICATION OF SIMIAN-VIRUS-40 ORIGIN-CONTAINING DNA DURING INFECTIONWITH A RECOMBINANT AUTOGRAPHA-CALIFORNICA MULTIPLE NUCLEAR POLYHEDROSIS-VIRUS EXPRESSING LARGE T-ANTIGEN

Autographica californica multiple nuclear polyhedrosis virus (AcMNPV h as been shown to encode many of the enzymes involved in the replicatio n of its own DNA. Although the AcMNPV genome contains multiple sets of reiterated sequences that are thought to function as origins of DNA r eplication, no initiator protein has yet been identified in the set of viral replication enzymes. In this study, the ability of a heterologo us origin initiator system to promote DNA replication in AcMNPV-infect ed cells was examined. A recombinant AcMNPV Chat expressed the simian virus 40 (SV40) large T antigen was surprisingly found to induce the e fficient replication of a transfected plasmid containing an SV40 origi n. This replication was subsequently found to involve three essential components: (i) T antigen, since replication of SV40 origin-containing plasmids was not induced by wild-type AcMNPV which did not express th is protein; (ii) an intact SV40 core origin, since deletion of specifi c functional motifs within the origin resulted in a loss of replicativ e abilities; and (iii) one or more AcMNPV-encoded proteins, since vira l superinfection,vas required for plasmid amplification. Characterizat ion of the replicated DNA revealed that it existed as a high-molecular -weight concatemer and underwent significant levels of homologous reco mbination between inverted repeat sequences. These properties were con sistent with an AcMNPV-directed mode of DNA synthesis rather than that of SV40 and suggested that T antigen-SV40 origin complexes may be cap able of initiating DNA replication reactions that can be completed by AcMNPV-encoded enzymes.