IDENTIFICATION OF A BACULOVIRUS GENE THAT PROMOTES AUTOGRAPHA-CALIFORNICA NUCLEAR POLYHEDROSIS-VIRUS REPLICATION IN A NONPERMISSIVE INSECT-CELL LINE

A gene that promotes Autographa californica hi nuclear polyhedrosis vi rus (AcMNPV) replication in IPLB-Ld652Y cells, a cell line that is non permissive for AcMNPV, was identified in Lymantria dispar M nuclear po lyhedrosis virus (LdMNPV). Cotransfection of AcMNPV DNA and a plasmid carrying the LdMNPV gene into LPLB-Ld652Y cells results in AcMNPV repl ication. The gene maps between 43.3 and 43.8 map units on the 162-kbp genome of LdMNPV. It comprises a 218-codon open reading frame and enco des a polypeptide with a predicted molecular mass of 25.7 kDa. The pre dicted polypeptide is glutamic acid and valine rich and negatively cha rged, with a pI of 4.61. No protein sequence motifs were identified, a nd no matches with known nucleotide or peptide sequences were found in the AcMNPV genome or database searches that suggest how this gene mig ht function. A recombinant AcMNPV bearing the LdMNPV gene overcomes a block in protein synthesis observed in AcMNPV-infected IPLB-Ld652Y cel ls. Using Southern blotting techniques, we were unable to identify a h omolog in Orgyia pseudotsugata M nuclear polyhedrosis virus, a baculov irus that is routinely propagated in IPLB-Ld652Y cells. This suggests that the LdMNPV host range gene is unique among the baculoviruses stud ied to date. We named this gene hrf-1 (for host range factor 1).