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DNA nicks inflicted by restriction endonucleases are repaired by a RecA‐ and RecB‐dependent pathway in Escherichia coli by Joseph Heitman; Tatyana Ivanenko; Antal Kiss is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

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Two mutants of the __Eco__RI endonuclease (R200K and E144C) predominantly nick only one strand of the DNA substrate. Temperature sensitivity of the mutant enzymes allowed us to study the consequences of inflicting DNA nicks at __Eco__RI sites __in vivo__. Expression of the __Eco__RI endonuclease mutants in the absence of the __Eco__RI methyltransferase induces the SOS DNA repair response and greatly reduces viability of __recA56__, __recB21__ and __lexA3__ mutant strains of __Escherichia coli__. In parallel studies, overexpression of the __Eco__RV endonuclease in cells also expressing the __Eco__RV methyltransferase was used to introduce nicks at non‐cognate __Eco__RV sites in the bacterial genome. __Eco__RV overproduction was lethal in __recA56__ and __recB21__ mutant strains and moderately toxic in a __lexA3__ mutant strain. The toxic effect of __Eco__RV overproduction could be partially alleviated by introduction into the cells of multiple copies of the __E. coli__ DNA ligase gene. These observations suggest that an increased number of DNA nicks can overwhelm the repair capacity of DNA ligase, resulting in the conversion of a proportion of DNA nicks into DNA lesions that require

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Author

Joseph Heitman; Tatyana Ivanenko; Antal Kiss

Publisher

John Wiley and Sons; Wiley (Blackwell Publishing); Blackwell Publishing Inc.; Wiley (ISSN 0950-382X)

Published

1999

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)