Zinc induces a bend within the transcription factor IIIA-binding region of the 5 S RNA gene.
Binding of Zn2+ to the 5 S RNA gene sequence of Xenopus borealis results in strong bending of the DNA, as inferred from transient electric birefringence data. The effect is specific for Zn2+; several other divalent ions are not able to induce a bend of a similar magnitude. Using five different fragments that span the binding sequence, we are able to estimate a bend magnitude of at least 55 degrees centered at base-pair +65 within the gene. This places the bend within the binding domain of the gene-regulatory protein transcription factor (TF) IIIA. Recent evidence has shown that the protein-DNA complex is also bent. Although our data do not allow us directly to link the two bends, our results suggest that TFIIIA could form a folded structure by stabilizing the same bent conformation that is induced by binding of Zn2+. The chemistry of Zn2+ binding to DNA, and the sequence around the bend center, suggest that the bend is most probably caused by joint co-ordination of Zn2+ to the N-7 groups of stacked purine residues.
Nickol
J
J
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Rau
D C
DC
D000818:Animals; D001483:Base Sequence; D001718:Birefringence; D002413:Cations, Divalent / Q000494:pharmacology; D004275:DNA, Ribosomal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D046911:Macromolecular Substances; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000378:metabolism*; D014981:Xenopus; D015032:Zinc / Q000494:pharmacology*
D002413:Cations, Divalent; D004275:DNA, Ribosomal; D046911:Macromolecular Substances; D008670:Metals; D012341:RNA, Ribosomal, 5S; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D015032:Zinc