The role oforiTintra-dependent enhanced recombination between mini-F-lac-oriTand λplac5

Abstract

SummaryRecombination between F42lacand λplac5is typically 20- to 50-fold more efficient than recombination between chromosomallacand λplac5. This enhancement of recombination isrecBCD-dependent and requires the expression of genes from thetraregulon of the F factor. Also required isoriT, the origin of F factor conjugational transfer, which must be located in-cisto the cellular copy oflac. In this study we show that enhanced recombination is not supported by anoriTpoint mutant that reducesoriTfunction in conjugation. We also present evidence that the activation oforiTfor recombination enhancement involves the same strand-specific nick that is required for conjugal DNA transfer. Although it is thought that the role oforiTin recombination enhancement is related to the facilitated entry of RecBCD enzyme into the DNA duplex, we were unable to detect any double-strand breakage atoriT.