Development of a novel enhanced baculovirus expression vector via promoter combination

Baculovirus expression systems (BESs) have been used to express many foreign proteins. BESs are known to be very suitable for foreign protein production due to the strong gene expression ability of the polyhedrin promoter. However, expression of foreign proteins using the polyhedrin promoter begins at a very late phase, in the last stage of viral infection. This causes insufficient production of foreign proteins due to death of the host cells. Therefore, our study aimed to construct a vector that can enable not only earlier production of foreign recombinant proteins but also increased production. For this purpose, a novel overexpression vector based on the polyhedrin promoter was constructed by using transcriptional enhancers (hr3 and repeated burst sequences (BSs)) and an additional promoter capable of inducing earlier gene expression than the polyhedrin promoter. Among the vectors with additional promoters that were evaluated, the overexpression vector with the p6.9 promoter showed the highest foreign protein expression efficiency. This vector showed approximately 94 times greater and one-day-earlier expression of the foreign protein than the control vector containing only the polyhedrin promoter. In order of greatest to least influence, the factors that increased the expression efficiency of the polyhedrin promoter were the repeated BSs, the p6.9 promoter and hr3.