MOLECULAR ANALYSIS OF AN ENHANCIN GENE IN THE LYMANTRIA-DISPAR NUCLEAR POLYHEDROSIS-VIRUS

A Lymantria dispar nuclear polyhedrosis virus (LdMNPV) gene has been i dentified that encodes a homolog to the granulovirus (GV) enhancin pro teins that are capable of enhancing the infection of other baculovirus es. Enhancin genes have been identified and sequenced for three specie s of GVs but have not been found in any other nuclear polyhedrosis vir us to date. The LdMNPV enhancin gene is located between 67.6 and 70.1 kbp on the viral genome. Northern and primer extension analyses of vir al RNAs indicate that the enhancin gene transcripts are expressed at l ate times postinfection from a consensus baculovirus late promoter. Th e LdMNPV enhancin exhibits 29% amino acid identity to the enhancin pro teins of the Trichoplusia ni, Pseudaletia unipuncta, and Helicoverpa a rmigera GVs. All four proteins contain a conserved zinc-binding domain characteristic of metalloproteases. A recombinant virus (enhnncin::ca t) was constructed in which the LdMNPV enhancin gene was inactivated b y insertion mutagenesis in order to ascertain the effect of the enhanc in protein on viral potency. The bioassay results indicate that disrup tion of the enhnncin gene in the LdMNPV results in a reduction in vira l potency.