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Hypermutability of homonucleotide runs in mismatch repair and DNA polymerase proofreading yeast mutants.

Authors
  • Tran, H T
  • Keen, J D
  • Kricker, M
  • Resnick, M A
  • Gordenin, D A
Type
Published Article
Journal
Molecular and cellular biology
Publication Date
May 01, 1997
Volume
17
Issue
5
Pages
2859–2865
Identifiers
PMID: 9111358
Source
Medline
License
Unknown

Abstract

Homonucleotide runs in coding sequences are hot spots for frameshift mutations and potential sources of genetic changes leading to cancer in humans having a mismatch repair defect. We examined frameshift mutations in homonucleotide runs of deoxyadenosines ranging from 4 to 14 bases at the same position in the LYS2 gene of the yeast Saccharomyces cerevisiae. In the msh2 mismatch repair mutant, runs of 9 to 14 deoxyadenosines are 1,700-fold to 51,000-fold, respectively, more mutable for single-nucleotide deletions than are runs of 4 deoxyadenosines. These frameshift mutations can account for up to 99% of all forward mutations inactivating the 4-kb LYS2 gene. Based on results with single and double mutations of the POL2 and MSH2 genes, both DNA polymerase epsilon proofreading and mismatch repair are efficient for short runs while only the mismatch repair system prevents frameshift mutations in runs of > or = 8 nucleotides. Therefore, coding sequences containing long homonucleotide runs are likely to be at risk for mutational inactivation in cells lacking mismatch repair capability.

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