In vivo selection of single-chain antibodies using a yeast two-hybrid system.

The current methodology for screening libraries of single-chain fragments of immunoglobulin variable domains (sFvs) utilizes bacterial phage systems. We have developed a unique in vivo selection protocol combining a modified yeast two-hybrid assay with a novel prey vector expressing sFvs. The viability of the system is demonstrated with the screen of a sFv library cloned into a yeast two-hybrid prey vector for molecules that target the bait ATF-2, a member of the CREB/ATF family of transcriptional regulatory proteins. The isolated sFv was capable of recognizing ATF-2 in vitro on Western blots and in vivo in mammalian cells.