DNA-bending finger: artificial design of 6-zinc finger peptides with polyglycine linker and induction of DNA bending.

DNA structural changes such as bending play an important role in various biological reactions. Not only protein binding to its specific DNA sequence but also DNA bending induced by the protein is indispensable for unique gene expression. Therefore, an artificial protein that induces a DNA conformational change is interesting as a transcriptional regulator of a specific gene. We created 6-zinc finger proteins, Sp1ZF6(Gly)n (n = 4, 7, 10), by connecting two DNA binding domains of transcription factor Sp1 with flexible polyglycine peptide linkers, and their effects on DNA structure were compared with that of native 3-zinc finger Sp1(530-623). Gel electrophoretic methods revealed that Sp1ZF6(Gly)7 and Sp1ZF6(Gly)10 bind to two distal GC boxes and result in DNA bending. Evidently, the hydroxyl radical footprinting analysis demonstrated that hypersensitive cleavage was observed at the 5'-TA step in the intervening region bound by Sp1ZF6(Gly)7 or Sp1ZF6(Gly)10. The phasing assays strongly suggested that the induced DNA bending was directed toward the major groove and that Sp1ZF6(Gly)7 caused the most drastic directional change in DNA bending. Of special interest are the facts that the newly designed 6-finger peptides Sp1ZF6(Gly)7 and Sp1ZF6(Gly)10 can induce DNA bending at the intervening region of the two distal binding sites and that the linker length between two 3-zinc finger motifs has a crucial effect on the entire DNA-bending direction. Such DNA-bending fingers may be feasible for use as a gene expression regulator based on the structural change in DNA in the future.