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Nearest neighbor influences on DNA polymerase insertion fidelity
L V Mendelman1, M S Boosalis, J Petruska
1Department of Biological Sciences, University of Southern California, Los Angeles 90089-1340.
The Journal of Biological Chemistry
|August 25, 1989
Summary
DNA polymerase alpha and avian myeloblastosis virus reverse transcriptase exhibit distinct error-making kinetics. Nearest-neighbor base stacking influences misinsertion hot spots differently for each enzyme, impacting DNA replication fidelity.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA polymerases and reverse transcriptases are crucial enzymes for DNA replication and repair.
- Understanding DNA polymerase error rates is essential for assessing genome stability and mutation accumulation.
- Nearest-neighbor base stacking influences DNA structure and enzyme-DNA interactions.
Purpose of the Study:
- To kinetically characterize single base substitution errors for Drosophila melanogaster DNA polymerase alpha and avian myeloblastosis virus reverse transcriptase.
- To evaluate the impact of nearest-neighbor base stacking on misinsertion kinetics at specific DNA sites.
- To compare the error-discrimination mechanisms of DNA polymerase alpha and reverse transcriptase.
Main Methods:
- Kinetics of misincorporation were measured for all possible single base substitution errors.
- Seventeen specific sites on bacteriophage M13 DNA were analyzed.
- Misinsertion frequencies were analyzed in relation to Km (Michaelis constant) and Vmax (maximum velocity) discrimination components.
Main Results:
- DNA polymerase alpha is more error-prone than reverse transcriptase, with similar rates for transitions and transversions, except for A.A and C.C mispairs.
- Reverse transcriptase shows lower efficiencies for transversions compared to transitions, particularly for A.G, G.G, and C.C mispairs.
- Misinsertion frequencies varied significantly based on location and nearest-neighbor base stacking, with distinct effects on Km and Vmax discrimination for both enzymes.
Conclusions:
- DNA polymerase alpha primarily uses Km discrimination for fidelity, while reverse transcriptase balances Km and Vmax discrimination.
- Nearest-neighbor base stacking has opposing effects on Km and Vmax discrimination components, influencing misinsertion hot spots.
- Pyrimidine nearest neighbors favor Km-based misinsertion, while purine nearest neighbors favor Vmax-based misinsertion, with effects potentially canceling when Km and Vmax components are similar.