Protein stitchery: Design of a protein for selective binding to a specific DNA sequence

We present a general strategy for designing proteins to recognize DNA sequences and illustrate this with an example based on the "Y-shaped scissors grip" model for leucine-zipper gene-regulatory proteins. The designed protein is formed from two copies, in tandem, of the basic (DNA binding) region of v-Jun. These copies are coupled through a tripeptide to yield a "dimer" expected to recognize the sequence TCATCGATGA (the v-Jun-v-Jun homodimer recognizes ATGACTCAT). We synthesized the protein and oligonucleotides containing the proposed binding sites and used gel-retardation assays and DNase I footprinting to establish that the dimer binds specifically to the DNA sequence TCATC-GATGA but does not bind to the wild-type DNA sequences, nor to oligonucleotides in which the recognition half-site is modified by single-base changes. These results also provide strong support for the Y-shaped scissors grip model for binding of leucine-zipper proteins.