The bountiful and baffling baculovirus: The story of polyhedrin transcription

Baculoviruses are a unique group of eukaryotic viruses that parasitize inse cts. The prototype member of the family Baculoviridae is Autographa califor nica multiple nuclear polyhedrosis virus (AcMNPV). Global interest in bacul ovirus biology stems from two important uses of baculoviruses - as biopesti cides and as a highly favoured eukaryotic expression system for the large-s cale production of recombinant proteins in the laboratory. Of late, baculov iruses 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 regulatio n of the hyperactive promoters used to drive foreign gene expression still remains shrouded in mystery. It is clear, however, that this regulation inv olves an intricate interplay of both host and viral factors. This review pr ovides an overview of what we do know about the mechanisms of transcription of baculoviral genes, with special emphasis on the polyhedrin promoter, th e workhorse promoter of the BEVS, and the insect cell host factors involved in enhancing transcription from it.