Efficiency and Fidelity of Site-Directed Mutagenesis with Complementary Primer Pairs

Area of Science:

• Molecular Biology
• Genetic Engineering
• Biotechnology

Background:

• QuickChange site-directed mutagenesis, using Pfu DNA polymerase and complementary primers, is widely used but shows variable efficiency.
• Newer P3a and P3b mutagenesis methods utilize partially overlapping primers with 3'-overhangs and advanced polymerases (SuperFi II, Q5) achieving ~100% efficiency.
• The potential of SuperFi II and Q5 polymerases to improve the existing QuickChange method remained unexplored.

Purpose of the Study:

• To evaluate if SuperFi II and Q5 polymerases enhance the efficiency of the QuickChange site-directed mutagenesis method.
• To compare the performance of the improved QuickChange method against the P3a and P3b mutagenesis strategies.
• To investigate the molecular mechanisms underlying mutagenesis efficiency differences.

Main Methods:

• Engineering 46 mutations across seven expression plasmids, including GC-rich sequences, using an adapted QuickChange protocol.
• Replacing Pfu DNA polymerase with SuperFi II or Q5 polymerases in the QuickChange protocol.
• Analyzing mutagenesis efficiency and identifying molecular errors, such as primer-derived insertions, in resulting plasmids.

Main Results:

• Replacing Pfu DNA polymerase with SuperFi II or Q5 reduced PCR length and increased QuickChange efficiency to 48%-69%, outperforming the original method.
• Despite improvement, the enhanced QuickChange method's efficiency was lower than that of the P3a/P3b methods utilizing 3'-overhang primers.
• Frequent insertions at primer sites, derived from primers, were observed in the improved QuickChange method, a phenomenon less common in P3a/P3b methods.

Conclusions:

• The study successfully improved the QuickChange site-directed mutagenesis method by incorporating advanced DNA polymerases.
• The findings confirm the superiority of primer pairs with 3'-overhangs (P3a/P3b methods) for achieving higher mutagenesis efficiency.
• A novel mechanism suggests that 3'-overhang primers enhance efficiency by minimizing primer-derived insertions at target sites.