A novel, inducible, eukaryotic gene expression system based on the quorum-sensing transcription factor TraR

Bacteria adapt their pattern of gene expression in response to a variety of external cues, including fluctuations in population density. This type of bacterial cell-to-cell communication is referred to as quorum-sensing. Quorum-sensing systems are present in many bacterial species and constitute a large collection of ligands and cognate receptors. The availability of such diversity offers interesting opportunities for biotechnological exploitation. We describe here the transformation of the quorum-sensing system of Agrobacterium tumefaciens into a transcription regulatory system that works in mammalian cells. The A. tumefaciens TraR protein was fused to the eukaryotic activation domain of NF-kappaB p65, generating a novel chimaeric transcriptional activator that stimulates gene transcription in different human cell lines from a minimal promoter containing the TraR DNA recognition sequence in the presence of the Agrobacterium quorum-sensing signal molecule N-(3-oxo-octanoyl)homoserine lactone (3-oxo-C-8-HSL). The basal level of transcription was low in the absence of 3-oxo-C-8-HSL, and gene expression was stimulated up to 1,000-fold at a saturating concentration of 3-oxo-C-8-HSL.