An Actin promoter drives expression of a multicistronic construct in which a single mRNA can give rise to three distinct fusion proteins, due to the presence of a 2A peptide between each of the three coding sequences. The first protein consists of mPlum tagged with a mitochondrial targeting signal (Tag:Mito(Unk)). The second protein corresponds to a fluorescent Lifeact-Ruby sensor that binds actin. The third protein corresponds to 'DBS-S', a Drice-based sensor of initiator caspase activity. The DBS-S sensor is a fusion protein composed of Tag:M(mCd8a) transmembrane domains, a mutated form of Drice that carries a C211A mutation in the catalytic site (rendering it inactive) and that is truncated such that only 16 amino acid residues remain after the the initiator caspase cleavage site TETD/G, and a fluorescent His2Av-GFP moiety. In the absence of caspase activation the fusion protein is tethered to the cellular membranes outside the nucleus (due to the Tag:M(mCd8a) tag). In the presence of an initiator caspase, the Drice sequence can be cleaved at the TETD/G site, releasing the His2Av-GFP moiety and allowing its translocation to the nucleus.