Inducible translocation trap: a system for detecting inducible nuclear translocation.

Here we report a general system, inducible translocation trap (ITT), for identification of proteins that translocate into the nucleus following signal transduction from cell surface receptors. ITT consists of a retroviral cDNA expression library of fusion proteins consisting of a LexA DNA binding domain, the transactivation domain of a transcriptional activator, and proteins encoded by cDNA inserts. The retroviral library is then transduced into cell lines containing a reporter gene with LexA binding sites in its promoter. Cells expressing the reporter gene by extracellular stimuli are then selected by flow-cytometric sorting. By using ITT, we identified cDNA encoding Stat1 in a screen of proteins which translocate into the nucleus by IFNgamma, indicating that this system can be used for isolation of nuclear translocating proteins induced by extracellular stimuli. ITT may be a useful tool for dissecting dynamic translocation in various biological systems.