The lacZ gene is often used as a reporter to monitor gene
expression. Assays for the lacZ gene product, β-galactosidase,
can be performed in numerous ways, including colorimetic assays
on filter-grown yeast colonies and enzymatic assays of cleared
yeast lysates. Here we describe using an enzymatic assay, the
Beta-Glo® Assay System, in which the addition of a single
reagent directly to yeast allows rapid quantitation of
β-galactosidase. In particular, we use the Beta-Glo® Assay
System with the yeast two- and three-hybrid systems. The yeast,
Saccharomyces cerevisiae, has become a vital tool for genetics,
molecular biology and biochemistry. The yeast two- and three-
hybrid systems are useful assays for identifying and analyzing
protein:protein and RNA:protein interactions ((1) ). In the
yeast two-hybrid system, when the fusion protein, Protein X-LexA
DNA binding domain, binds the fusion protein, Protein
Y-transcription activation domain, lacZ , is transcribed (Figure
1, Panel A). This allows analysis of direct pr