IDENTIFICATION AND CHARACTERIZATION OF LEF-1, A BACULOVIRUS GENE INVOLVED IN LATE AND VERY LATE GENE-EXPRESSION

An Autographa californica nuclear polyhedrosis virus (AcMNPV) gene req uired in transient expression assays for late and very late viral gene expression was identified, sequenced, and transcriptionally mapped. T his gene, designated late expression factor 1 (lef-1), was located bet ween 7.4 and 8.7 map units of the AcMNPV physical map. It was identifi ed by cotransfecting Spodoptera frugiperda cultured cells with a colle ction of overlapping cloned DNA fragments covering the entire AcMNPV g enome and a reporter gene controlled by an early, late, or very late A cMNPV promoter. Omission of the DNA fragment containing lef-1 curtaile d most late and very late gene expression but not early gene expressio n. lef-1 was found to be an early gene transcribed as a 1.8-kb RNA in the presence of the protein synthesis inhibitor cycloheximide. The C t erminus of the predicted polypeptide product, LEF-1, contained a seque nce motif characteristic of nucleoside triphosphate-binding sites.