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Mol. Cell. Biol., 05 1997, 2851-2858, Vol 17, No. 5
EA Sia, RJ Kokoska, M Dominska, P Greenwell and TD Petes
We examined the stability of microsatellites of different repeat unit
lengths in Saccharomyces cerevisiae strains deficient in DNA mismatch
repair. The msh2 and msh3 mutations destabilized microsatellites with
repeat units of 1, 2, 4, 5, and 8 bp; a poly(G) tract of 18 bp was
destabilized several thousand-fold by the msh2 mutation and about 100- fold
by msh3. The msh6 mutations destabilized microsatellites with repeat units
of 1 and 2 bp but had no effect on microsatellites with larger repeats.
These results argue that coding sequences containing repetitive DNA tracts
will be preferred target sites for mutations in human tumors with mismatch
repair defects. We find that the DNA mismatch repair genes destabilize
microsatellites with repeat units from 1 to 13 bp but have no effect on the
stability of minisatellites with repeat units of 16 or 20 bp. Our data also
suggest that displaced loops on the nascent strand, resulting from DNA
polymerase slippage, are repaired differently than loops on the template
strand.
Copyright © 1997, American Society for Microbiology
Microsatellite instability in yeast: dependence on repeat unit size and DNA mismatch repair genes
Department of Biology and Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill 27599-3280, USA.
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