IDENTIFICATION AND CHARACTERIZATION OF THE ECDYSTEROID UDP-GLUCOSYLTRANSFERASE GENE OF THE LYMANTRIA-DISPAR MULTINUCLEOCAPSID NUCLEAR POLYHEDROSIS-VIRUS

We have located, cloned, sequenced and characterized the ecdysteroid U DP-glucosyltransferase gene (egt) gene from the baculovirus Lymantria dispar multinucleocapsid nuclear polyhedrosis virus.(LdMNPV), which is specific for the gypsy moth (L. dispar). The egt gene from the relate d baculovirus Autographa californica multinucleocapsid nuclear polyhed rosis virus (AcMNPV) disrupts the hormonal balance of the host larva b y galactosylating ecdysone, which prevents moulting. The location of t he LdMNPV egt gene, determined by hybridization analysis using a clone d coding segment of the AcMNPV egt gene, was mapped to between 79.1 an d 80.2 map units on the viral genome. This region contains an open rea ding frame of 1464 nucleotides capable of encoding a 55K polypeptide. This predicted protein exhibits a 42% amino acid identity with the AcM NPV egt polypeptide. Transcripts of the egt gene were analysed by Nort hern blot and primer extension. The egt gene is transcribed from appro ximately 12 to 48 h, and maximally at about 16h post-infection. Transc ription occurred in the presence of aphidicolin, a viral DNA synthesis inhibitor, but not in the presence of cycloheximide, a protein synthe sis inhibitor. Therefore the LdMNPV egt gene is classified as a delaye d early gene. The egt gene is transcribed in a clockwise direction wit h respect to the circular map, and transcription initiates at a single site. Comparisons between the two baculoviral egt proteins and mammal ian UDP-glucuronosyltransferases reveal areas which are conserved betw een the mammalian and baculoviral genes, as well as areas that are onl y conserved in the viral egt proteins. The LdMNPV protein sequence app ears to include a signal peptide, which would allow the protein to be secreted into the haemolymph.