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Site-directed mutagenesis using positive antibiotic selection
1Medical College of Wisconsin, Milwaukee 53226-0509, USA. bohnsack@post.its.mcw.edu
Abstract:
Various mutagenesis protocols have been established that use the hybridization of a mismatched oligonucleotide to prime DNA synthesis on an M13 phagemid template. For efficient mutagenesis, all of these methods require a means to select for the mutant strand before or during amplification in an Escherichia coli host. In the Altered Sites II protocol, the mismatched oligonucleotide and an oligonucleotide that restores antibiotic resistance to the phagemid are simultaneously hybridized to the template and coupled by DNA synthesis and ligation. The restored antibiotic resistance is then used to select only those phagemids which incorporate the antibiotic repair oligonucleotide. Generally, between 60 and 90% of the phagemids recovered will incorporate both oligonucleotides. This method provides a simple an efficient technique for introducing specific mutations into DNA.
Insights
This study introduces the Altered Sites II protocol for efficient DNA mutagenesis. The method uses antibiotic resistance selection to ensure high recovery rates of desired mutations in M13 phagemids.
Area of Science:
- Molecular Biology
- Genetic Engineering
- Biotechnology
Background:
- Oligonucleotide-directed mutagenesis is crucial for genetic studies.
- Existing mutagenesis methods require efficient selection of mutant DNA strands.
- M13 phagemid systems are commonly used for DNA manipulation.
Purpose of the Study:
- To develop a simple and efficient method for introducing specific mutations into DNA using M13 phagemids.
- To improve the selection process for mutant DNA strands during mutagenesis.
Main Methods:
- The Altered Sites II protocol involves simultaneous hybridization of a mismatched oligonucleotide and an antibiotic resistance-restoring oligonucleotide to an M13 phagemid template.
- DNA synthesis and ligation are used to incorporate both oligonucleotides.
- Selection is based on restored antibiotic resistance in Escherichia coli host cells.
Main Results:
- The Altered Sites II protocol achieves efficient mutagenesis by coupling mutation introduction with antibiotic resistance restoration.
- Between 60% and 90% of recovered phagemids incorporate both introduced oligonucleotides.
- This method simplifies the selection of desired mutant DNA.
Conclusions:
- The Altered Sites II protocol offers a robust and straightforward technique for site-directed mutagenesis.
- The reliance on antibiotic resistance provides a clear selection marker for successful mutagenesis.
- This method enhances the efficiency of generating specific DNA mutations.