GFP-based constructs and methods for detecting apoptosis

This invention provides a fluorescent protein construct to detect protease or caspase activated apoptosis. The construct contains a donor fluorescent protein; an acceptor fluorescent protein; and a linker peptide, wherein the linker peptide comprises a substrate sequence of a caspase. The linker peptide is position between the donor and acceptor proteins. This invention also provides nucleic acids encoding the fluorescent protein construct, expression constructs comprising the nucleic acids as well as gene delivery vehicles containing these nucleic acids. These compositions are useful in a method for detecting caspase activated programmed cell death or apoptosis by culturing a sample of host cells containing the nucleic acids and/or proteins described above under conditions suitable for excitation of the donor fluorescent protein and detecting the fluorescence property in the sample, wherein the presence of programmed cell death in the cells of the sample results in a change in the degree of fluorescence resonance energy transfer between the donor protein and the acceptor protein.