A recombination-efficient baculovirus vector for simultaneous expression of multiple genes.

The baculovirus system is an extremely powerful tool for expression of heterologous genes in eukaryotic environment. A multiple expression vector, pBacUCmP3, was constructed which harbored two copies of the Autographa californica nuclear polyhedrosis virus very late gene promoter and the Drosophila melanogaster 70-kDa heat-shock protein (hsp70) promoter with downstream unique restriction sites for cloning of three independent foreign genes. Co-transfection of pBacUCmP3 with Bsu36I-linearized viral DNA yields recombinant progeny viruses at very high frequencies. The utility of this multiple expression transfer vector was demonstrated using three heterologous reporter genes encoding the beta-subunit of the human chorionic gonadotropin hormone, firefly luciferase and the bacterial beta-galactosidase (beta Gal) enzyme. The expression of reporter genes, monitored at various times post-infection, confirmed that while beta-Gal synthesis was under the transcriptional control of the hsp70 promoter, the beta hCG and Luc proteins were synthesized as a function of polyhedrin promoter activation profile. This vector will be useful for multiple synthesis of proteins at different time points.