Immediate-Early Baculovirus Genes Transactivate the p143 Gene Promoter of Autographa californica Nuclear Polyhedrosis Virus

Abstract

Trans-acting regulatory components of Autographa californica nuclear polyhedrosis virus (AcMNPV) were studied in a transient assay system for their ability to activate the p143 gene promoter. A region including 502 nt upstream of the AUG of the p143 gene was linked to the bacterial chloramphenicol acetyltransferase (CAT) gene. The p143 promoter-CAT construct was used to identify AcMNPV immediate-early gene products required for expression from the p143 gene early promoter. Transient expression assays in uninfected Spodoptera frugiperda cells indicated that the IE-1 gene product was capable of transactivating the p143 gene promoter and this activation was augmented by the IE-N gene product. In addition, another immediate-early gene, PE-38, was shown to mediate transactivation of the p143 gene promoter but not the 39K delayed early gene promoter. Deletions to -187 bp relative to the p143 RNA start site did not significantly affect promoter activity in the combined presence of IE-1 and the HindIII-F fragment. However, a deletion to -52 bp decreased promoter activity by 40%. In contrast, in the presence of ts8 DNA at 33°, deletions to -52 bp decreased promoter activity by 80% suggesting that additional viral factors were involved in p143 gene promoter regulation.