The terminal DNA structure of mammalian chromosomes.
In virtually all eukaryotic organisms, telomeric DNA is composed of a variable number of short direct repeats. While the primary sequence of telomeric repeats has been determined for a great variety of species, the actual physical DNA structure at the ends of a bona fide metazoan chromosome with a centromere is unknown. It is shown here that an overhang of the strand forming the 3' ends of the chromosomes, the G-rich strand, is found at mammalian chromosome ends. Moreover, on at least some telomeres, the overhangs are > or = 45 bases long. Such surprisingly long overhangs were present on chromosomes derived from fully transformed tissue culture cells and normal G0-arrested peripheral leukocytes. Thus, irrespective of whether the cells were actively dividing or arrested, a very similar terminal DNA arrangement was found. These data suggest that the ends of mammalian and possibly all vertebrate chromosomes consist of an overhang of the G-rich strand and that these overhangs may be considerably larger than previously anticipated.
McElligott
R
R
Dept. de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbrooke, QC, Canada.
Wellinger
R J
RJ
D000818:Animals; D001483:Base Sequence; D002461:Cell Line, Transformed; D004247:DNA / Q000737:chemistry*; D004261:DNA Replication; D004277:DNA, Single-Stranded; D006367:HeLa Cells; D006801:Humans; D008322:Mammals; D051379:Mice; D009690:Nucleic Acid Conformation; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000737:chemistry*
D004277:DNA, Single-Stranded; D004247:DNA; D019098:Telomerase