Use of Early Baculovirus Promoters for Continuous Expression and Efficient Processing of Foreign Gene Products in Stably Transformed Lepidopteran Cells

Abstract

Baculoviruses are currently used as vectors for the transient high-level expression of foreign gene products in insect cells. In this study, we demonstrate that baculoviruses can also be made to continuously express a foreign gene product by using the promoter from IE1, an immediate early viral gene, to produce stably-transformed insect cells. This approach gave levels of foreign gene expression lower than those usually obtained with the lytic baculovirus expression vector system. Expression, however, was continuous and stable, and a complex human glycoprotein (tissue plasminogen activator) was processed more efficiently. We conclude that stable transformation is a feasible approach for baculovirus-mediated foreign gene expression in lepidopteran cells, particularly for products that are relatively poorly-expressed and/or processed in lytically infected cells.

High-level expression of secreted glycoproteins in transformed lepidopteran insect cells using a novel expression vector

“…However, the use of promoters weaker than late or very late baculovirus promoters results in lower final recombinant protein yields. The generation of transformed lepidopteran cells expressing foreign proteins continuously has also been reported (Jarvis et al, 1990;Joyce et al, 1993). Thus far, protein yields obtained from transformed insect cells have also been considerably lower than those usually obtained from baculovirus-infected cells.…”

Temporal nature of the promoter and not relative strength determines the expression of an extensively processed protein in a baculovirus system

“…This has important implications in using the MP or similar promoters activated earlier in the infection cycle [29] for the expression of highly processed proteins since the use of a strong promoter does not necessarily confer any advantage by virtue of its strength [30] in such situations. This approach of temporal expression can be successfully used to produce more efficiently similar proteins, of biomedical and therapeutic uses, which require extensive post-translational modifications and processing for their bioactivity.…”

Gene targeting in the silkworm by use of a baculovirus

“…However, gene expression is transient, because the infected cells ultimately die from virus infection and the polyhedrin promoter is expressed only during the very late phase of infection. For this reason, the IE1 promoter from NPV (Jarvis et al 1990;Jarvis 1993) or a densovirus promoter (Giraud et al 1992) has been utilized for stable transformation of lepidopteran cells and constitutive expression of foreign genes. Attempts to develop similar transient expression systems in silkmoths have failed, because plasmid DNAs injected into silkworm eggs were rapidly degraded (Nagaraju et al 1996).…”