A BACULOVIRUS EXPRESSION VECTOR DERIVED FROM THE BASIC-PROTEIN PROMOTER OF AUTOGRAPHA-CALIFORNICA NUCLEAR POLYHEDROSIS-VIRUS

The basic protein of Autographa californica nuclear polyhedrosis virus (AcMNPV) is associated with virus DNA in virion nucleocapsids and is produced in infected cells during the late phase of gene expression. A transfer vector was constructed containing the β-galactosidase gene, under the control of a copy of the putative basic protein promoter, in place of the polyhedrin gene within the AcMNPV EcoRI fragment I. After cotransfection of Spodoptera frugiperda cells with the transfer vector and infectious AcMNPV DNA, polyhedrin-negative recombinant viruses were selected which expressed high levels of β-galactosidase. Radiolabelling of infected cell proteins showed that β-galactosidase was expressed at the same time as the viral basic protein, between 8 to 24 h post-infection, with a peak synthesis at 12 to 15 h. These results demonstrated that the temporal regulation of the basic protein promoter was not affeted by its position within the virus genome. Furthermore, a new baculovirus vector system is now available for high level expression of foreign genes at earlier times in infected cells.