Unilateral ends-out gene targeting increases mistargeting through supporting extensive single-strand assimilation

Area of Science:

• Molecular Biology
• Genetics
• Yeast as a model organism

Background:

• Ends-out gene targeting, a method for allele replacement via homologous recombination, has significant fundamental and applied implications.
• Understanding the precise mechanisms of homologous recombination in gene targeting is crucial for its effective application.

Purpose of the Study:

• To investigate the mechanisms underlying ends-out gene targeting in Saccharomyces cerevisiae.
• To differentiate between unilateral and bilateral targeting pathways and their respective frequencies.
• To elucidate the role of strand assimilation in targeting accuracy and mistargeting.

Main Methods:

• Development of an experimental system in yeast to quantify unilateral and bilateral targeting outcomes.
• Quantitative analysis of genetic outcomes to infer targeting pathway probabilities.
• Comparative analysis across different experimental setups.
• Comprehensive qualitative analysis to reveal the underlying gene targeting mechanism.

Main Results:

• Quantitative analysis initially indicated predominant bilateral targeting.
• A subsequent analysis suggested a prevalence of unilateral targeting, raising questions about experimental artifacts.
• A unified model of ends-out gene targeting involving two intertwined pathways was proposed.
• Bilateral targeting was suggested to minimize mistargeting by limiting strand assimilation.

Conclusions:

• Ends-out gene targeting operates via a single fundamental mechanism with two distinct pathways for homologous invasion initiation.
• Bilateral targeting may enhance accuracy by restricting strand assimilation, contrasting with unilateral targeting's potential for extensive assimilation and mistargeting.
• The findings provide a deeper understanding of homologous recombination and gene targeting mechanisms.