A multisite-directed mutagenesis using T7 DNA polymerase: application for reconstructing a mammalian gene

Area of Science:

• Molecular Biology
• Genetic Engineering

Background:

• Gene reconstruction and mutagenesis are crucial for protein engineering and functional studies.
• Existing methods can be inefficient or limited in their ability to introduce multiple modifications simultaneously.

Purpose of the Study:

• To describe and validate a novel method for multisite-directed mutagenesis and gene reconstruction.
• To demonstrate the efficiency and applicability of this method using a porcine growth hormone (pGH) cDNA model.

Main Methods:

• Utilized a single oligodeoxyribonucleotide and a high-processivity DNA polymerase (modified T7 DNA polymerase).
• Applied the method to reconstruct a eukaryotic cDNA for porcine growth hormone (pGH), introducing a 75 bp deletion and a G-to-A transition.
• Compared the efficacy of modified T7 DNA polymerase against T4 DNA polymerase and Klenow fragment.

Main Results:

• Achieved maximum mutation frequency within 15 minutes with an efficiency approaching 50% using modified T7 DNA polymerase.
• Successfully deleted 75 bp and introduced a G-to-A transition, creating a new PvuII restriction site in the pGH gene.
• Observed no multisite-directed mutants when using T4 DNA polymerase or Klenow fragment, highlighting the specificity of modified T7 DNA polymerase.

Conclusions:

• The described method enables efficient and rapid introduction of multiple mutations and gene reconstruction.
• Modified T7 DNA polymerase is highly effective for multisite-directed mutagenesis, offering advantages over other polymerases.
• This technique is versatile and applicable to both simple single-site mutations and complex gene engineering strategies.