Identification of the very early transcribed baculovirus gene PE-38

Abstract

We have started to identify early viral RNAs that are transcribed at 1 h after inoculation to investigate the mechanism involved in the regulation of early gene expression of Autographa californica nuclear polyhedrosis virus (AcNPV). Cloned viral DNA fragments were hybridized to Northern (RNA) blots of polyadenylated RNA isolated from Spodoptera frugiperda cells at 1, 2, and 6 h postinfection to localize very early transcripts. Subsequently we prepared a cDNA library of polyadenylated RNA transcribed at 1 h after inoculation to analyze the cDNA clones corresponding to the major early RNAs. We identified a gene located upstream of the immediate-early gene IE-N extending in the opposite direction. Because of the very early expression during AcNPV infection and the transient expression in uninfected cells, we conclude that we found an immediate-early gene, designated PE-38. The determination of the nucleotide sequence of PE-38 revealed one open reading frame potentially encoding a gene product of 38 kDa. Results of in vitro translation experiments suggest that a PE-38-specific polypeptide of approximately 38 kDa can be expressed. We have evidence from computer analyses that the predicted amino acid sequence includes two putative DNA-binding motifs, a zinc finger, and a leucine zipper.