Zinc finger proteins, of the type first discovered in transcription factor IIIA
(TFIIIA), are one of the largest and most important families of DNA-binding
proteins. The crystal structure of a complex containing the five Zn fingers from
the human GLI oncogene and a high-affinity DNA binding site has been determined
at 2.6 A resolution. Finger one does not contact the DNA. Fingers two through
five bind in the major groove and wrap around the DNA, but lack the simple,
strictly periodic arrangement observed in the Zif268 complex. Fingers four and
five of GLI make extensive base contacts in a conserved nine base-pair region,
and this section of the DNA has a conformation intermediate between B-DNA and
A-DNA. Analyzing the GLI complex and comparing it with Zif268 offers new
perspectives on Zn finger-DNA recognition.
