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In vitro DNA synthesis by DNA polymerase I and DNA polymerase alpha on single-stranded DNA containing either purine
J S Hoffmann1, E Moustacchi, G Villani
1Laboratoire de Pharmacologie et de Toxicologie Fondamentales du CNRS, Toulouse, France.
Abstract:
The capacity of the large fragment of DNA polymerase I from Escherichia coli and of DNA polymerase alpha from Drosophila embryo to replicate single-stranded M13mp10 DNA containing either purine or pyrimidine monoadducts was compared. The monoadducts were respectively induced by cisplatinum and by furocoumarin photoaddition. For both types of lesions, it is observed that the eukaryotic enzyme is more inhibited than the prokaryotic one. By mapping the arrest sites produced by furocoumarin monoadducts on the synthesis catalysed by DNA polymerase alpha, we show that, in contrast with the photoreaction observed with double-stranded DNA, these compounds do not show a strong sequence specificity in reacting with single-stranded DNA.
Insights
Eukaryotic DNA polymerase alpha is more inhibited by DNA adducts than the prokaryotic DNA polymerase I. Furocoumarin adducts on single-stranded DNA lack sequence specificity, unlike on double-stranded DNA.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA polymerases are crucial for DNA replication and repair.
- DNA adducts can impede polymerase activity, potentially leading to mutations.
- Understanding how different polymerases handle DNA damage is vital for comprehending genome stability.
Purpose of the Study:
- To compare the replication capacity of Escherichia coli DNA polymerase I (large fragment) and Drosophila melanogaster DNA polymerase alpha on single-stranded DNA containing monoadducts.
- To investigate the effect of cisplatinum and furocoumarin photoaddition-induced monoadducts on DNA synthesis.
- To determine the sequence specificity of furocoumarin adducts on single-stranded DNA.
Main Methods:
- Replication assays using single-stranded M13mp10 DNA.
- Induction of monoadducts using cisplatinum and furocoumarin photoaddition.
- Mapping of polymerase arrest sites on synthesized DNA strands.
Main Results:
- Both DNA polymerase I and DNA polymerase alpha showed reduced replication capacity in the presence of DNA adducts.
- The eukaryotic DNA polymerase alpha was more sensitive to inhibition by both types of monoadducts compared to the prokaryotic DNA polymerase I.
- Furocoumarin monoadducts on single-stranded DNA did not exhibit strong sequence specificity in polymerase arrest sites, contrasting with observations on double-stranded DNA.
Conclusions:
- Eukaryotic DNA polymerase alpha is more susceptible to inhibition by DNA monoadducts than prokaryotic DNA polymerase I.
- The lack of sequence specificity for furocoumarin adducts on single-stranded DNA suggests different lesion recognition mechanisms compared to double-stranded DNA.
- These findings contribute to understanding differential DNA repair and replication fidelity across species.