An artifact in studies of gene regulation using β-galactosidase reporter gene assays.

Reporter gene assays are important tools for evaluating gene expression. A frequently used assay measures the activity of β-galactosidase (β-gal) expressed from lacZ in plasmid or genomic constructions. Such constructions are often used to interrogate the ability of DNA (query DNA), potentially encoding a transcription factor, to regulate in trans the expression of a promoter fused to the reporter lacZ. Query DNA is frequently inserted into a second plasmid within the α-subunit of β-gal, interrupting its function. However, this plasmid can induce up-expression of β-gal even when void of query DNA, leading to confusion between artifact and authentic regulation.