Recent work has shown that it is possible to target regulatory elements to DNA 
sequences of an investigator's choosing, increasing the armamentarium for 
probing gene function. In this review, we discuss the development and use of 
designer zinc finger proteins (ZFPs) as sequence specific tools. While the main 
focus of this review is to discuss the attachment of the FokI nuclease to ZFPs 
and the ability of the resulting fusion protein (termed zinc finger nucleases 
(ZFNs)) to genomically manipulate a gene of interest, we will also cover the 
utility of other functional domains, such as transcriptional activators and 
repressors, and highlight how these are being used as discovery and therapeutic 
tools.