The bountiful and baffling baculovirus: the story of polyhedrin transcription

Abstract

Baculoviruses are a unique group of eukaryotic viruses that parasitize insects. The prototype member of the family Baculoviridae is Autographa californica multiple nuclear polyhedrosis virus (AcMNPV). Global interest in baculovirus biology stems from two important uses of baculoviruses - as biopesticides and as a highly favoured eukaryotic expression system for the large-scale production of recombinant proteins in the laboratory. Of late, baculoviruses have invited renewed interest by virtue of their potential use as a delivery system in gene therapy. Although the baculovirus expression vector system (BEVS) is extensively used worldwide, the transcriptional regulation of the hyperactive promoters used to drive foreign gene expression still remains shrouded in mystery. It is clear, however, that this regulation involves an intricate interplay of both host and viral factors. This review provides an overview of what we do know about the mechanisms of transcription of baculoviral genes, with special emphasis on the polyhedrin promoter, the workhorse promoter of the BEVS, and the insect cell host factors involved in enhancing transcription from it.