Type I restriction enzyme with RecA protein promotes illegitimate recombination
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Updated: Aug 30, 2026

In Vitro Directed Evolution of a Restriction Endonuclease with More Stringent Specificity
Published on: March 25, 2020
Kohji Kusano1, Yasuo Asami, Ayumi Fujita
1Department of Molecular Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Abstract:
Illegitimate (non-homologous) recombination requires little or no sequence homology between recombining DNAs and has been regarded as being a process distinct from homologous recombination, which requires a long stretch of homology between recombining DNAs. However, we have found a type of illegitimate recombination that requires an interaction between long homologous DNA sequences. It was detected when a plasmid that carried 2-kb-long inverted repeats was subjected to type I (EcoKI) restriction in vivo within a special mutant strain of Escherichia coli. In the present work, we analyzed genetic requirements for this type of illegitimate recombination in well-defined genetic backgrounds. Our analysis demonstrated dependence on RecA function and on the presence of two EcoKI sites on the substrate DNA. These results are in harmony with a model in which EcoKI restriction enzyme attacks an intermediate of homologous recombination to divert it to illegitimate recombination.
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