DNA Polymerase Delta Synthesizes Both Strands during Break-Induced Replication

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Genetics

Background:

• Break-induced replication (BIR) is a homology-directed repair pathway for one-ended DNA breaks, crucial for genomic stability.
• BIR involves a migrating D-loop and conservative synthesis, distinct from standard replication.
• The specific DNA polymerases responsible for synthesizing both DNA strands during BIR remain largely uncharacterized.

Purpose of the Study:

• To elucidate the roles of replicative DNA polymerases, specifically DNA polymerase delta (Pol δ) and epsilon (Pol ε), in synthesizing DNA during BIR.
• To determine whether a single polymerase or multiple polymerases are involved in replicating the invading and complementary strands during BIR.

Main Methods:

• Utilized mutant alleles of replicative DNA polymerases permissive for ribonucleotide incorporation.
• Employed hydrolytic end sequencing to identify polymerase signatures within the genome.
• Assessed the impact of Pol δ and Pol ε depletion on BIR efficiency in cellular models.

Main Results:

• Demonstrated that DNA polymerase delta (Pol δ) is responsible for replicating both the invading and complementary strands during BIR.
• Showed that depletion of Pol δ significantly impairs BIR.
• Found that depletion of DNA polymerase epsilon (Pol ε) has no discernible effect on BIR.

Conclusions:

• DNA polymerase delta (Pol δ) is the primary polymerase responsible for DNA synthesis throughout the Break-induced replication (BIR) process.
• The findings clarify the polymerase usage in a critical DNA repair pathway, highlighting Pol δ's essential role.