Metal-induced infidelity during DNA synthesis.

Area of Science:

• Biochemistry
• Molecular Biology
• Toxicology

Background:

• DNA replication accuracy is crucial for genomic stability.
• Divalent cations are essential cofactors for DNA polymerases.
• The specific impact of certain cations on polymerase fidelity is not fully understood.

Purpose of the Study:

• To investigate the effects of various divalent cations on DNA replication accuracy in vitro.
• To elucidate the mechanism by which beryllium ions (Be2+) affect DNA polymerase fidelity.

Main Methods:

• In vitro DNA synthesis assays using purified avian myeloblastosis virus DNA polymerase.
• Analysis of DNA synthesis products using equilibrium density centrifugation and snake venom phosphodiesterase hydrolysis.
• Nearest neighbor analysis to identify types of base substitution errors.
• Enzyme pretreatment and glycerol gradient centrifugation to study Be2+-DNA polymerase interactions.

Main Results:

• Only Be2+ significantly altered DNA replication accuracy across all templates and nucleotides tested.
• Be2+-induced errors were primarily single base substitutions incorporated via phosphodiester bonds.
• Pretreatment of the enzyme, not the template, with Be2+ enhanced error frequency.
• Dissociation of the Be2+-DNA polymerase complex restored normal polymerase fidelity.

Conclusions:

• Weak binding of metal cations, specifically Be2+, to DNA polymerase can significantly impair DNA replication accuracy.
• The Be2+-induced alteration of DNA polymerase fidelity offers a potential screening system for chemical mutagens and carcinogens.