In Vitro Mutagenesis Protocols

Volume 634 of the series Methods in Molecular Biology pp 421-430


En Passant Mutagenesis: A Two Step Markerless Red Recombination System

  • B. Karsten TischerAffiliated withInstitut für Virologie, Freie Universität Berlin Email author 
  • , Gregory A. SmithAffiliated withDepartment of Microbiology-Immunology, Northwestern University
  • , Nikolaus OsterriederAffiliated withInstitut für Virologie, Freie Universität BerlinDepartment of Microbiology and Immunology, Cornell University

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Bacterial artificial chromosomes are used to maintain and modify large sequences of different origins in Escherichia coli. In addition to RecA-based shuttle mutagenesis, Red recombination is commonly used for sequence modification. Since foreign sequences, such as antibiotic resistance genes as well as frt- or loxP-sites are often unwanted in mutant BAC clones, we developed a Red-based technique that allows for the scarless generation of point mutations, deletions, and insertion of smaller and larger sequences. The method employs a sequence duplication that is inserted into the target sequence in the first recombination step and the excision of the selection marker by in vivo I-SceI cleavage and the second Red recombination. To allow for convenient and highly efficient mutagenesis without the use of additional plasmids, the E. coli strain GS1783 with a chromosomal encoded inducible Red- and I-SceI-expression was created.

Key words

Red recombination BAC Markerless En passant mutagenesis I-SceI