The stabilization of repetitive tracts of DNA by variant repeats requires a functional DNA mismatch repair system.
Simple repetitive tracts of DNA are unstable in all organisms thus far examined. In the yeast S. cerevisiae, we show that a 51 bp poly(GT) tract alters length at a rate of about 10(-5) per cell division. Insertion of a single variant repeat (either AT or CT) into the middle of the poly(GT) tract results in 100-fold stabilization. This stabilization requires the DNA mismatch repair system. Alterations within tracts with variant repeats occur more frequently on one side of the interruption than on the other. The stabilizing effects of variant repeats and polarity of repeat alterations have also been observed in trinucleotide repeats associated with certain human diseases.
Heale
S M
SM
Department of Biology, University of North Carolina at Chapel Hill 27599-3280, USA.
Petes
T D
TD
D001483:Base Sequence; D004260:DNA Repair / Q000235:genetics*; D004259:DNA-Directed DNA Polymerase / Q000502:physiology; D005838:Genotype; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D015003:Yeasts / Q000235:genetics
D004259:DNA-Directed DNA Polymerase