engleski

SSB protein preserves genome stability in Escherichia coli

Preserving genome stability is of critical importance to living organisms. Lack of genome stability results in severe conditions such as cancer and premature aging in mammals. Stability of E. coli genome is determined by metabolism of 3´-ending tails at DNA double-strand breaks, which are faithfully mended by homologous recombination catalyzed by RecBCD enzyme. The rare cases of aberrant DNA transactions that lead to imprecise recombination events in wild-type E. coli are unwound by prototypic genome guardian, RecQ helicase, thus preventing the appearance of illegitimate recombination. We used ssb-1 conditional mutation and measured the frequency of aberrant λ-prophage excision from the E. coli genome (Spi- assay) for quantifying illegitimate recombination in the bacteria of wild-type as well as of several other E. coli genetic backgrounds. We reveal that SSB protein prevents illegitimate recombination, which depends on SSB binding to ssDNA. Since for illegitimate recombination SSB overproduction complements RecQ deficiency, our results suggest that SSB prevents appearance of aberrant recombination events, whereas RecQ dismantles those that do occur in the E. coli genome.

SSB ; genome stability ; illegitimate recombination ; Spi- assay

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