Break-induced replication is highly inaccurate.

Area of Science:

• Molecular Biology
• Genetics
• DNA Repair

Background:

• DNA synthesis is crucial for genome duplication and repair.
• While DNA replication is accurate, DNA repair synthesis can be error-prone.
• Break-induced replication (BIR) is a process mimicking replication but initiated at double-strand breaks (DSBs).

Purpose of the Study:

• To quantify mutagenesis associated with BIR in Saccharomyces cerevisiae.
• To investigate the factors contributing to BIR-related inaccuracies.
• To understand the implications of BIR mutagenesis in cellular processes.

Main Methods:

• Utilized frameshift reporter systems to measure mutagenesis during BIR.
• Assessed mutation rates at varying distances from the DSB.
• Investigated the roles of polymerase proofreading, mismatch repair, and dNTP levels.

Main Results:

• BIR DNA synthesis is intrinsically inaccurate, with frameshift mutation rates up to 2,800-fold higher than normal replication.
• High mutagenesis rates were observed both near and far from the DSB.
• Elevated dNTP levels contributed to BIR-related mutagenesis.
• Polymerase proofreading and mismatch repair partially corrected BIR errors, with Pol δ identified as a major error generator.

Conclusions:

• High levels of DNA polymerase errors, inadequately corrected, drive mutagenesis during BIR.
• BIR activation in eukaryotes may significantly contribute to mutation accumulation, impacting cancer and evolution.
• Understanding BIR's mutagenic potential is crucial for comprehending genome instability and evolutionary processes.