DIFFERING ROLES FOR ZINC FINGERS IN DNA RECOGNITION - STRUCTURE OF A 6-FINGER TRANSCRIPTION FACTOR IIIA COMPLEX

The crystal structure of the six NH2-terminal zinc fingers of Xenopus laevis transcription factor IIIA (TFIIIA) bound with 31 bp of the 5S r RNA gene promoter has been determined at 3.1 Angstrom resolution. Indi vidual zinc fingers are positioned differently in the major groove and across the minor groove of DNA to span the entire length of the duple x. These results show how TFIIIA can recognize several separated DNA s equences by using fewer fingers than necessary for continuous winding in the major groove.