Design and selection of novel Cys(2)His(2) zinc finger proteins

Cys(2)His(2) zinc finger proteins offer a stable and versatile framework fo r the design of proteins that recognize desired target sites on double-stra nded DNA. Individual fingers from these proteins have a simple beta beta al pha structure that folds around a central zinc ion, and tandem sets of fing ers can contact neighboring subsites of 3-4 base pairs along the major groo ve of the DNA. Although there is no simple, general code for zinc finger-DN A recognition, selection strategies have been developed that allow these pr oteins to be targeted to almost any desired site on double-stranded DNA. Th e affinity and specificity of these new proteins can also be improved by li nking more fingers together or by designing proteins that bind as dimers an d thus recognize an extended site. These new proteins can then be modified by adding other domains-for activation or repression of transcription, for DNA cleavage, or for other activities. Such designer transcription factors and other new proteins will have important applications in biomedical resea rch and in gene therapy.