Colony Lift Colorimetric Assay for beta-Galactosidase Activity

In this protocol, we present a qualitative assay for monitoring the level of expression of beta-galactosidase, an enzyme encoded by the LacZ gene, in yeast. This is useful both for determining autoactivity of LacZ expression in yeast DNA bait strains and for assessing LacZ reporter gene activation mediated by a transcription factor prey interaction with a DNA bait of interest in yeast one-hybrid (Y1H) assays. In this colorimetric assay, yeast are lysed in liquid nitrogen and then assayed for beta-galactosidase expression using the colorless compound X-gal, which turns blue in the presence of this enzyme