Monovalent cation-induced structure of telomeric DNA: the G-quartet model.
We have investigated the structures formed by oligonucleotides composed of two or four repeats of the telomeric sequences from Oxytricha and Tetrahymena. The Oxytricha four-repeat molecule (d(T4G4)4 = Oxy-4) forms structures with increased electrophoretic mobility in nondenaturing gels containing Na+, K+, or Cs+, but not in gels containing Li+ or no added salt. Formation of the folded structure results in protection of a set of dG's from methylation by dimethyl sulfate. Efficient UV-induced cross-links are observed in Oxy-4 and the related sequence from Tetrahymena (d(T2G4)4 = Tet-4), and join thymidine residues in different repeats. Models proposed to account for these data involve G-quartets, hydrogen-bonded structures formed from four guanosine residues in a square-planar array. We propose that the G-quartet structure must be dealt with in vivo by the telomere replication machinery.
Williamson
J R
JR
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, Boulder, Colorado 80309.
Raghuraman
M K
MK
Cech
T R
TR
D000818:Animals; D001483:Base Sequence; D002875:Chromosomes / Q000648:ultrastructure*; D004247:DNA / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure*; D004591:Electrophoresis, Polyacrylamide Gel; D056890:Eukaryota / Q000235:genetics; D008745:Methylation; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis; D013768:Tetrahymena / Q000235:genetics; D014466:Ultraviolet Rays
D009838:Oligodeoxyribonucleotides; D004247:DNA