IDENTIFICATION AND FUNCTIONAL-ANALYSIS OF A NON-HR ORIGIN OF DNA-REPLICATION IN THE GENOME OF SPODOPTERA-EXIGUA MULTICAPSID NUCLEOPOLYHEDROVIRUS

The genome of Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMN PV) was screened for the presence of putative origins of DNA replicati on (oris), Using a transient DNA replication assay, several fragments were identified that underwent SeMNPV-dependent DNA replication in Spo doptera frugiperda cells (Sf-AE-21). Preliminary sequence data reveale d the presence of multiple copies of homologous repeats (hrs). Restric tion fragment Xbal-F2 showed a distinct sequence reminiscent of Autogr apha californica and Orgyia pseudotsugata MNPV (AcMNPV and OpMNPV) non -hr oris. Deletion analysis of this fragment indicated that the essent ial sequences of this putative non-hr ori mapped within a region of 80 0 bp. Sequence analysis of this region showed a unique distribution of six different (im)perfect palindromes, several polyadenylation motifs and the occurrence of multiple direct repeats, No sequence homology o r similarities to other reported baculovirus oris were detected. The s patial and modular distribution of these motifs are similar to those o f the non-hr oris of AcMNPV and OpMNPV. Comparison of baculovirus non- hr and consensus eukaryotic oris revealed no consensus ori but indicat ed that each of the non-hrs studied so far is unique. From the structu ral similarity, however, it was concluded that the SeMNPV Xbal-F2 ori represents a baculovirus non-hr type ori, In addition, evidence is pro vided that SeMNPV renders more specificity to baculovirus DNA replicat ion than AcMNPV.