title: Poly(dG)-poly(dC) sequences, under torsional stress, induce an altered DNA conformation upon neighboring DNA sequences.
abstract: Supercoiled plasmid DNAs (at bacterial superhelical density) harboring the homopurine-homopyrimidine sequence, poly(dG)-poly(dC), were reacted with bromoacetaldehyde (BAA), a reagent that reacts with unpaired DNA bases. Not only did the poly(dG)-poly(dC) sequence react with BAA but, surprisingly, neighboring sequences located 3' to the contiguous G sequences also reacted. The altered conformation in the poly(dG)-poly(dC) sequence and in the neighboring sequence occurred in the same supercoiled plasmid DNA molecule. Furthermore, the occurrence of an "unpaired" conformation in the neighboring sequence is strictly due to a positional effect, since it is observed when the poly(dG)-poly(dC) segment is adjacent to a variety of neighboring sequences.
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D004278:DNA, Superhelical; D004591:Electrophoresis, Polyacrylamide Gel; D009690:Nucleic Acid Conformation / Q000187:drug effects; D010957:Plasmids; D011089:Polydeoxyribonucleotides
chemical_list: D004278:DNA, Superhelical; D011089:Polydeoxyribonucleotides; C038235:bromoacetaldehyde; C016681:poly(dG).poly(dC); D000079:Acetaldehyde