DNA polymerases are error-prone at RecA-mediated recombination intermediates

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Genetic studies suggest Y-family DNA polymerase IV (DinB) causes mutations during stress-induced double-strand break (DSB) repair via recombination-directed replication (RDR).
• Previous work showed pol IV is recruited to D-loop intermediates and is mutagenic during RDR in vitro, supporting its role in stress-induced mutagenesis.

Purpose of the Study:

• To investigate the fidelity of DNA polymerases at D-loop recombination intermediates.
• To determine if other DNA polymerases, besides pol IV, exhibit error-prone activity at D-loops.

Main Methods:

• In vitro assays examining DNA polymerase activity at RecA-mediated D-loop structures.
• Comparative analysis of DNA polymerase IV (DinB) and DNA polymerase I fidelity.

Main Results:

• DNA polymerase IV (DinB) is confirmed to be error-prone at D-loops during RDR, particularly under stress conditions.
• Surprisingly, A-family DNA polymerase I, typically high-fidelity, also demonstrates high error rates at D-loops.
• Both polymerases exhibit error-prone activity at these critical recombination intermediates.

Conclusions:

• DNA polymerases appear intrinsically error-prone when acting at RecA-mediated D-loops.
• Auxiliary factors are likely essential for suppressing mutations and ensuring high-fidelity DNA synthesis during RDR in proliferating cells under normal conditions.