Identification and Analysis of a Putative Origin of DNA Replication in the Choristoneura fumiferana Multinucleocapsid Nuclear Polyhedrosis Virus Genome

Abstract A recombinant plasmid containing the Choristoneura fumiferana multinucleocapsid nuclear polyhedrosis virus (CfMNPV) Hind III R fragment (m.u. 2.2-3.9) was shown to undergo CfMNPV infection-dependent DNA replication in Cf-124T cells. Replication of this DNA sequence was detectable by 24 hr p.i. and did not appear to have resulted as a consequence of recombination with the virus genome. Replication was inhibited by mimosine, an inhibitor of eukaryotic DNA replication. These data suggest that Hind III R of CfMNPV DNA contains an origin of DNA replication which we call ori 1. Hind III R contains five GC-rich and three AT-rich regions and a 0.9-kb homologous repeat region 1 ( hr 1). Two short 440- and 740-bp contiguous sequences at the right end of the Hind III R fragment separately exhibited limited ori function. Hind III R subfragments with optimal ori activity contained a cluster of repeated and inverted sequences including nine copies of a 50-bp homologous repeat sequence ( hr 1a to hr 1i) within hr 1. The CfMNPV hr 1 sequence was somewhat homologous with the homologous repeat ( hr ) of the putative Autographa californica MNPV (AcMNPV) replication origins. Hind III Y, another CfMNPV DNA fragment containing an hr sequence, hr 3, also supported infection-dependent DNA replication, suggesting that it too contains an ori . Although replication of a putative AcMNPV origin ( Hind III Q) was detectable in CfMNPV-infected Cf-124T cells, replication of CfMNPV Hind III R was not detectable in AcMNPV-infected Spodoptera frugiperda cells.