Ubi-p63E regulatory sequences drive expression of a caspase-inducible form of GAL4. The construct encodes a fusion protein consisting of Mmus\Cd8a and the GAL4 coding region, separated by the caspase-3-binding and cleavage domain of Diap1 (amino acid residues 2-147, with residues 21 and 22 mutated from NN to GV, in order to protect the cleaved product from possible N-end rule degradation). In the absence of caspase, the Mmus\Cd8a sequence tethers GAL4 to the plasma membrane, rendering it inactive. In the presence of caspase, the fusion protein is cleaved at the DQVD site in the Diap1 sequence, releasing the GAL4 coding region so that in can enter the nucleus and drive transcription.