title: Cationic metals promote sequence-directed DNA bending.
abstract: A DNA segment of approximately 200 base pairs (bp) from Crithidia fasciculata kinetoplast minicircles was previously shown by electron microscopy (EM) to bend into a small circle due to its unique nucleotide sequence containing repeated blocks of 4-6 A's. When this segment was flanked by 207 bp of plasmid DNA on one side and 460 bp on the other, the resulting 890-bp DNA was found to appear either relatively straight or extremely bent as visualized by EM. The bend was located one-third the distance from one end. The fraction of molecules with the most extreme bend increased from approximately 2% to 50-60% following incubation of the DNA with increasing concentrations of Zn2+, Co2+, Ba2+, and Mn2+. These observations suggest that sequence-directed bending in DNA is an inducible and not a static phenomenon. Possible roles of transitions between the bent and straight conformations in the control of gene expression are discussed.
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D001483:Base Sequence; D002412:Cations / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology; D003421:Crithidia / Q000235:genetics; D004247:DNA / Q000187:drug effects / Q000648:ultrastructure*; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D015032:Zinc / Q000494:pharmacology
chemical_list: D002412:Cations; D001464:Barium; D003035:Cobalt; D004247:DNA; D008274:Magnesium; D015032:Zinc