MOLECULAR MECHANISMS OF INTRAMOLECULAR RECOMBINATION-DEPENDENT RECIRCULARIZATION OF LINEARIZED PLASMID DNA IN ESCHERICHIA-COLI - REQUIREMENTS FOR THE RUVA, VUVB, RECG, RECF AND RECR GENE-PRODUCTS

Intramolecular recombinogenic recircularization (IRR) of linearized pl asmid DNA was used to study mechanistic relationships between recombin ation functions in Escherichia coli in vivo. Homology requirement for IRR ranges from 1 to 11 bp, and does not exhibit any notable strain to strain variability, with recombination occurring at a large number of possible sites within the plasmid molecule. We show that recF- and re cR-deficient strains exhibit greatly reduced IRR efficiency, although neither gene product is totally essential. Mutation of recF and recR d oes not alter the distribution of recombination sites nor the range of molecules produced during IRR. A recO-deficient strain did not exhibi t dramatic reduction in efficiency of IRR, implying that RecF and RecR proteins maintain function during this mechanism in the absence of fu nctional RecO. The main IRR mechanism is ruvA-, ruvB- and recG-depende nt and there is a lower efficiency second IRR mechanism operating in r uvA, ruvB and recG mutants. Some evidence suggests that this second me chanism involves functions associated with the replisome.