Figure 4.

Expression of caspase inhibitors suppresses caspase-dependent reporter activation in yeast. The LexA/β-gal reporter strain carrying pGALL-CLBDG6 was transformed with either an empty pCUP1 plasmid or pCUP1-CED-3 and either an empty pGALL vector or pGALL-p35. Three colonies from each transformation were grown for 24 hr in selective gal/raf medium. Cultures were diluted 1:10 into fresh gal/raf medium containing 3 μM copper sulfate and were grown for a further 10 hr, after which o-nitrophenyl-β-d-galactoside assays for β-gal activity were performed. Cultures from caspase transformants showed significant β-gal activity, which was suppressed by GALL-dependent expression of baculovirus p35 (A). In an experiment similar to that described in A, expression of caspase 7⁵³ was induced in cells that express baculovirus p35 or the mouse IAP MIHA. Expression of caspase 7⁵³ resulted in a significant increase in cellular β-gal activity, which was suppressed by GALL-dependent expression of p35 or MIHA (B).