NMR Structure of Transcription Factor Sp1 DNA Binding Domain,

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Abstract
To understand the DNA recognition mechanism of zinc finger motifs of transcription factor Sp1, we have determined the solution structure of DNA-binding domain of the Sp1 by solution NMR techniques. The DNA-binding domain of Sp1 consists of three Cys2His2-type zinc finger motifs. They have typical ββα zinc finger folds and relatively random orientations. From DNA-binding analysis performed by NMR and comparison between structures determined here and previously reported structures of other zinc fingers, it was assumed that DNA recognition modes of fingers 2 and 3 would be similar to those of fingers of Zif268, in which each finger recognizes four base pairs strictly by using residues at positions −1, 2, 3, and 6 of the recognition helix. On the contrary, finger 1 can use only two residues for DNA recognition, Lys550 and His553 at positions −1 and 3 of the helix, and has more relaxed sequence and site specificity than other Cys2His2 zinc fingers. It is proposed that this relaxed property of finger 1 allows transcription factor Sp1 to bind various DNA sequences with high affinity.