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Adaptive mutation by deletions in small mononucleotide repeats
S M Rosenberg1, S Longerich, P Gee
1Department of Biochemistry, University of Alberta Faculty of Medicine, Edmonton, Canada.
Science (New York, N.Y.)
|July 15, 1994
Summary
Adaptive mutation in Escherichia coli occurs via -1 deletions in repeat regions, suggesting DNA polymerase errors and deficient mismatch repair are key mechanisms. This finding challenges sequence transfer models for adaptive mutation.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Adaptive mutation allows organisms to adapt to environmental changes.
- Homologous recombination functions are known to be involved in adaptive reversion of frameshift mutations.
Purpose of the Study:
- To investigate the molecular mechanisms underlying adaptive reversion of a +1 frameshift mutation in Escherichia coli.
- To determine if recombinational mechanisms or DNA polymerase errors are responsible for adaptive mutation.
Main Methods:
- Analysis of -1 deletion patterns in mononucleotide repeat regions.
- Comparison of mutation patterns with those in yeast and human hereditary colon cancer cells.
- Assessment of the role of homologous recombination and mismatch repair in adaptive mutation.
Main Results:
- Adaptive reversion occurred via -1 deletions within small mononucleotide repeats.
- This pattern supports DNA polymerase errors over sequence transfer mechanisms.
- Similar mutation patterns were observed in yeast and mismatch repair-deficient human cells.
Conclusions:
- A recombinational mechanism for adaptive mutation involving polymerase errors that escape mismatch repair is proposed.
- The findings suggest a conserved mechanism for adaptive mutation across different organisms.
- Deficiency in post-synthesis mismatch repair plays a crucial role in adaptive mutation.