THE SINGLE CYS(2)-HIS(2) ZINC-FINGER DOMAIN OF THE GAGA PROTEIN FLANKED BY BASIC RESIDUES IS SUFFICIENT FOR HIGH-AFFINITY SPECIFIC DNA-BINDING

Specific DNA binding to the core consensus site GAGAGAG has been shown with an 82-residue peptide (residues 310-391) taken from the Drosophi la transcription factor GAGA. Using a series of deletion mutants, it w as demonstrated that the minimal domain required for specific binding (residues 310-372) includes a single zinc finger of the Cys(2)-His(2) family and a stretch of basic amino acids located on the N-terminal en d of the zinc finger, In gel retardation assays, the specific binding seen with either the peptide or the whole protein Is zinc dependent an d corresponds to a dissociation constant of approximate to 5 x 10(-9) M for the purified peptide. It has previously been thought that a sing le zinc finger of the Cys(2)-His(2) family is incapable of specific, h igh-affinity binding to DNA. The combination of an N-terminal basic re gion with a single Cys(2)-His(2) zinc finger in the GAGA protein can t hus be viewed as a novel DNA binding domain. This raises the possibili ty that other proteins carrying only one Cys(2)-His(2) finger are also capable of high-affinity specific binding to DNA.