CHARACTERIZATION OF A ZINC-DEPENDENT TRANSCRIPTIONAL ACTIVATOR FROM ARABIDOPSIS

The C-2-H-2 zinc-finger is a widely occurring DNA binding motif, usual ly present as tandem repeats, The majority of C-2-H-2 zinc-finger prot eins that have been studied are derived from animals, Here, we charact erize a member of a distinct class of plant C-2-H-2 zinc-finger protei ns in detail, A cDNA clone encoding a DNA binding protein from Arabido psis was isolated by SouthWestern screening, The protein, termed ZAP1 (Zinc-dependent Activator Protein-1), is encoded by a single copy gene , which is expressed to similar levels in root and flower, to a somewh at lower level in stem and to low levels in leaf and siliques, The opt imal binding site was determined by random binding site selection, and the consensus sequence found is CGTTGACCGAG, The homology between ZAP 1 and other DNA binding proteins is restricted to a repeated region of a stretch of 24 highly conserved amino acids followed by a zinc-finge r motif (C-X(4)-C-X(22-23)-H-X(1)-H) The C-terminal zinc-finger region is essential for DNA binding, whereas deletion of the N-terminal one resulted in 2.5-fold reduced binding affinity, Binding of ZAP1 to DNA was abolished by metal-chelating agents, The activation domain as dete rmined in yeast is adjacent to and possibly overlapping with the DNA b inding domain, Particle bombardment experiments with plant cells showe d that ZAP1 increases expression of a gusA reporter gene that is under control of ZAP1 binding sites, We conclude that ZAP1 is a plant trans criptional activator with a C-2-H-2 zinc-finger DNA binding domain.