recA-independent DNA Recombination between Repetitive Sequences: Mechanisms and Implications

Publisher Summary This chapter discusses the distinct features of recA -independent recombination among repetitive sequences in bacteria, with special emphasis on replicational models and their implications in related processes such as genome rearrangement and gene amplification in eukaryotic cells. In Escherichia coli , general (or homologous) recombination typically involves extensive stretches of sequence homology and is dependent on the RecA protein and other recombination functions. Site-specific recombination occurs at highly preferred sites and requires special proteins other than RecA and other activities involved in general recombination. Intramolecular reciprocal exchange among direct repeats can lead to the deletion of one of the repeats and any intervening sequence, whereas intermolecular unequal crossover can result in deletion in one of the products and addition in the other. These processes can be accomplished by RecA-mediated general homologous recombination. It has been shown that efficient recA -independent recombination can also occur at direct repeats, resulting in deletion and addition, which are sometimes accompanied by other rearrangement(s). recA -independent recombination is most efficient when the direct repeats are in close proximity and it can form products different from that of recA -dependent homologous recombination.