PathHunter® Nuclear Translocation cell lines are engineered to co-express two fusion proteins: a) Enzyme Donor (ED) tagged target protein; b) an Enzyme Acceptor (EA) tagged TAZ domain, derived from the CBP/P300 transcription factor, that localizes to the nucleus. Depending on the assay, activation of the signaling pathway can either a) induce translocation of the ED-tagged target protein into the nucleus, which will force complementation of the two enzyme fragments, and result in the formation of a functional enzyme that will hydrolyze substrate and generate a chemiluminescent signal; or b) induce the ED-tagged protein to vacate the nucleus, resulting in a decrease of functional enzyme and a subsequent decrease of chemiluminescent signal. Some nuclear translocation assays will also co-express an untagged secondary protein involved in the pathway of interest.