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Efficiency of correct nucleotide insertion governs DNA polymerase fidelity
William A Beard1, David D Shock, Brian J Vande Berg
1Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
The Journal of Biological Chemistry
|October 9, 2002
Summary
DNA polymerases with low fidelity are inefficient, but their error rate stems from efficient correct nucleotide insertion, not incorrect ones. This suggests low fidelity polymerases evolved for replicating damaged DNA.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA polymerase fidelity is crucial for accurate DNA replication and repair.
- Fidelity is defined by the polymerase's ability to select correct nucleoside triphosphates (dNTPs).
- Low fidelity DNA polymerases are often associated with DNA repair processes.
Purpose of the Study:
- To investigate the relationship between DNA synthesis efficiency and error rates in low fidelity DNA polymerases.
- To analyze the kinetic properties of correct and incorrect dNTP insertion in various DNA polymerases.
- To understand the evolutionary basis of low fidelity DNA polymerases.
Main Methods:
- Analysis of dNTP insertion efficiency for DNA polymerase beta mutants (R283A, G274P).
- Comparative study of exonuclease-deficient DNA polymerases from five different biological families.
- Quantification of fidelity using specificity constants for correct and incorrect dNTPs.
Main Results:
- A strong correlation was found between DNA synthesis ability and the likelihood of base substitution errors.
- The difference between low and high fidelity polymerases is primarily due to the efficiency of correct nucleotide insertion.
- Catalytically inefficient mutants (R283A) showed reduced fidelity, but another inefficient mutant (G274P) did not, indicating inefficiency does not always equate to low fidelity.
Conclusions:
- Low fidelity DNA polymerases are characterized by efficient correct nucleotide insertion, not inefficient incorrect insertion.
- Inefficiency in DNA polymerases does not necessarily lead to low fidelity.
- Low fidelity polymerases may represent an evolutionary adaptation for replicating damaged DNA or repair intermediates without compromising genomic integrity.