title: S1 nuclease sensitivity of a double-stranded telomeric DNA sequence.
abstract: We examined structural properties of poly d(C4A2).d(T2G4), the telomeric DNA sequence of the ciliated protozoan Tetrahymena. Under conditions of high negative supercoiling, poly d(C4A2).d(T2G4) inserted in a circular plasmid vector was preferentially sensitive to digestion with S1 nuclease. Only the C4A2 strand was sensitive to first-strand S1 cutting, with a markedly skewed pattern of hypersensitive sites in tracts of either 46 or 7 tandem repeats. Linear poly d(C4A2).(T2G4) showed no preferential S1 sensitivity, no circular dichroism spectra indicative of a Z-DNA conformation, no unusual Tm, and no unusual migration in polyacrylamide gel electrophoresis. The S1 nuclease sensitivity properties are consistent with a model proposed previously for supercoiled poly d(CT).d(AG) (Pulleyblank et al., Cell 42:271-280, 1985), consisting of a double-stranded, protonated, right-handed underwound helix. We propose that this structure is shared by related telomeric sequences and may play a role in their biological recognition.
authors.forename: M
authors.initials: M
authors.lastname: Budarf
authors.forename: E
authors.initials: E
authors.lastname: Blackburn
mesh_terms: D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D004720:Endonucleases / Q000494:pharmacology*; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012091:Repetitive Sequences, Nucleic Acid; D015719:Single-Strand Specific DNA and RNA Endonucleases
chemical_list: D004247:DNA; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases