THE DEVELOPMENT OF BETA-LACTAMASE AS A HIGHLY VERSATILE GENETIC REPORTER FOR EUKARYOTIC CELLS

We describe in this report that TEM-1 beta-lactamase has several desir able characteristics as a genetic reporter. First, it has no endogenou s counterpart in eukaryotic cells and therefore provides a background- free measure of gene expression. Second, because of the uniqueness of the substrate cleavage reaction, a wide variety of substrates which ar e efficiently cleaved can be synthesized for beta-lactamase. Third, si nce the assays involve no more than addition of substrate to media, it is possible to continuously monitor a culture without destruction of the cells. Fourth, the enzyme is extremely versatile in that it can be fused to other proteins and retain activity. To demonstrate the versa tility of beta-lactamase, we created three forms of the enzyme includi ng secreted, intracellular, and membrane-bound forms of the enzyme, ea ch form having distinct advantages as a reporter system. We also showe d that levels of secreted beta-lactamase were proportional to both the levels of transfected DNA, beta-lactamase mRNA, as well as activity o f the chloramphenicol acetyl transferase gene controlled by the same p romoter, validating the reliability of this reporter. beta-Lactamase t hus represents a novel and highly versatile genetic reporter. (C) 1997 Academic Press.