Two Distinct Pathways Support Gene Correction by Single-Stranded Donors at DNA Nicks.

Area of Science:

• Molecular Biology
• Genetics
• Genomics

Background:

• DNA nicks represent the most frequent type of DNA damage.
• Understanding DNA nick repair is crucial for maintaining genomic stability and advancing genome engineering technologies.

Purpose of the Study:

• To define the distinct pathways involved in homology-directed repair (HDR) utilizing single-stranded DNA donors at nicks.
• To elucidate the role of RAD51 in these repair pathways and its impact on genomic stability.

Main Methods:

• Investigated DNA repair mechanisms at nicks and double-strand breaks using single-stranded DNA donors.
• Analyzed the influence of RAD51 on homology-directed repair and mutagenic end joining pathways.

Main Results:

• Identified two novel pathways for homology-directed repair at nicks: one involving annealing-driven strand synthesis and another relying on annealing-driven heteroduplex correction.
• Demonstrated that RAD51 inhibits homology-directed repair and mutagenic end joining at nicks, but is largely independent of these processes at double-strand breaks.
• Established guidelines for designing targets and donors for gene correction based on the defined repair pathways.

Conclusions:

• Naturally occurring DNA nicks possess significant recombinogenic and mutagenic potential.
• RAD51 plays a critical role in suppressing the mutagenic potential of nicks, thereby contributing to genomic stability.
• The findings provide insights into optimizing gene correction strategies and understanding DNA repair networks.