RecBC and RecF recombination pathways and the induced precise excision of Tn10 in Escherichia coli

Mitomycin C (MMC) treatment or mutations in uvrD enhance the frequency of T n10 precise excision, We have shown previously that several repair-recombin ation genes, such as recA, ruv and recF are involved in the induced excisio n process. In this study, we find that other genes belonging to the RecBC a nd RecF sexual recombination pathways also participate in this process sinc e mutations in recB, sbcB or recO diminish, though to different degrees, th e frequency of Tn10 precise excision induced by MMC treatment or by uvrD mu tants. Pairwise combinations of some of these mutations were also tested fo r Tn10 induced precise excision; most of these double mutants showed additi ve effects in reducing the frequency of the excision process, The results o f these studies suggest that recombinational-repair genes, particularly rec F, sbcB and recO have different roles in the induced excision of Tn10 than in recombinational mating. (C) 1999 Elsevier Science B.V. All rights reserv ed.