Impact of the exonuclease vii on the reckless DNA degradation in the recA mutants in Escherichia coli bacterium

Protein RecA ima ključnu ulogu u homolognoj rekombinaciji kod bakterije Escherichia coli. Stanice recA mutanata pokazuju značajan pad vijabilnosti, gubitak sposobnosti za rekombinaciju i sklonost neobuzdanoj degradaciji DNA. U ovom radu je proučavan utjecaj inaktivacije gena xseA (koji kodira egzonukleazu VII) na neobuzdanu degradaciju DNA u recA mutantima. Učinak mutacije xseA praćen je zasebno i u kombinaciji s mutacijama xonA i sbcD, koje inaktiviraju egzonukleazu I, odnosno nukleazu SbcCD. Degradacija DNA je praćena tijekom normalnog rasta stanica i nakon izlaganja UV-zračenju. Za praćenje degradacije DNA korištene su mikroskopske metode i elektroforeza u promjenjivom električnom polju. Rezultati su pokazali da inaktivacija egzonukleaze VII, egzonukleaze I i nukleaze SbcCD ima sinergistički učinak i dokida neobuzdanu degradaciju DNA u stanicama recA mutanata.RecA protein has a major role in homologous recombination in Escherichia coli. Cells mutated in recA gene show decreased cell viability, homologous recombinaton deficiency and tendency for reckless DNA degradation. The aim of this work was to study the effect of the xseA mutation (that inactivates exonuclease VII) on reckless DNA degradation in recA mutants. Effect of xseA mutation was examined separately as well as in combination with xonA and sbcD mutations, which inactivate exonuclease I and SbcCD nuclease, respectively. DNA degradation was followed in normally growing as well as in UV-irradiated cells, by microscopic methods and by pulsed-field gel electrophoresis. The results have shown that inactivation of exonuclease VII, exonuclease I and SbcCD nuclease has sinergistic effect and abolishes reckless DNA degradation in recA mutant cells