Development of a Reporter Gene: Expression of the Fused lux Gene in Escherichia coli, Yeast and COS-7 Cells

To develop a useful reporter gene system that could be used to monitor promoter activity not only in vitro but also in vivo, the fused structural genes of bacterial luciferase (luxA, luxB) from a marine bacterium, Vibrio harveyi, was expressed in Eschericha coli, yeast, and COS-7 cells. Furthermore, a 2.0 kb HindIII gene cassette of the lux was constructed by introducing two J7mdIII sites flanking the open reading frame to facilitate future cloning of the lux gene. Escherichia coli cells harboring the lux gene cassette in a plasmid emitted light when the substrate decanal was supplied as vapor. The repression and induction of the yeast promoter GAL1 was monitored with the lux gene cassette as a reporter gene by measuring the amount of light from yeast cells taken from culture. This result opens up the possibility of assaying a promoter without disrupting yeast cells. The fused lux gene under the control of either the chicken β-actin or the CMV promoter was expressed very well in COS-7 cells. However, the expressed luciferase was only able to be assayed from crude extracts of COS-7 cells.