engleski

Effects of a recG mutation on homologous recombination and DNA repair in recBC sbcBC mutants of Escherichia coli

RecG protein is a DNA helicase that promotes DNA strand exchange and heteroduplex extension during homologous recombination in Escherichia coli. Cells mutated in the recG gene show moderate recombination deficiency and increased UV-sensitivity compared to the wild type cells. We have studied the effects of recG mutation on recombinational DNA repair after exposure to UV-irradiation, on conjugal recombination, and on cell morphology in two types of recBC sbcBC mutants of E. coli. In one mutant, the sbcB gene was inactivated by point mutation (sbcB15), while in other it was completely deleted (delsbcB). We found that introduction of the recG mutation in recBC sbcB15 sbcC background strongly reduced the efficiency of recombination and recombinational DNA repair, and caused severe defects in chromosome segregation and cell division. On the contrary, in recBC delsbcB sbcC background, the recG mutation had relatively mild effect on both recombination processes and cell morphology. We inferred that the sbcB15 mutation modifies the recombinational process in a way that the process becomes more dependent on the RecG protein. It is possible that the mutant SbcB15 protein binds to recombinogenic 3' DNA ends and interferes with the processing of recombination intermediates in the absence of RecG protein.

Escherichia coli; homologous recombination; DNA repair; recG; sbcB

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