Different contributions of three zinc fingers of transcription factor Sp1 to DNA recognition: novel binding mode of N-terminal finger 1.

To clarify binding properties of the first zinc finger of Sp1, finger 1, to GC-box DNA, two-finger mutant peptides Sp1 (zf12) and Sp1 (zf23) were created and their DNA binding characteristics have been compared with those of native three-zinc finger protein Sp1. Some gel electrophoretic experiments involving DNase I footprinting and gel mobility shift assays reveal that finger 1 is not essential to sequence-specific DNA recognition, but moderately contributes to total binding affinity and overall sequence specificity by three zinc fingers of Sp1.