engleski

Roles of ExoI and SbcCD nucleases in "reckless" DNA degradation in recA mutants of Escherichia coli

Exponentially growing recA mutant cells of Escherichia coli display pronounced spontaneous DNA degradation that starts at the sites of DNA damage, and depends on the RecBCD nuclease (ExoV) activity. As a consequence of this "reckless" DNA degradation, populations of recA mutants contain a large proportion of anucleate cells. We have found that both DNA degradation and anucleate cell production are efficiently suppressed by mutations in xonA (sbcB) and sbcD genes. The suppressive effect of these mutations was observed in normally grown, as well as in UV-irradiated, recA cells. The products of xonA and sbcD genes are known to code for ExoI and SbcCD nucleases, respectively. Since both xonA and sbcD mutations are required for strong suppression of DNA degradation while individual mutations have only a weak suppressive effect, we infer that ExoI and SbcCD play partially redundant roles in regulating DNA degradation in recA cells. We suggest that their role might be in processing (blunting) DNA ends, thereby producing suitable substrates for RecBCD binding.

Escherichia coli ; recA mutants ; DNA degradation ; ExoI ; SbcCD

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