Chi-Dependent Intramolecular Recombination in Escherichia coli

Corresponding author: Amikam Cohen, Department of Molecular Biology, The Hebrew University-Hadassah Medical School, Jerusalem 91010, Israel, amikamc{at}cc.huji.ac.il (E-mail).

Communicating editor: L. S. SYMINGTON

Homologous recombination in Escherichia coli is enhanced by a cis-acting octamer sequence named Chi (5'-GCTGGTGG-3') that interacts with RecBCD. To gain insight into the mechanism of Chi-enhanced recombination, we recruited an experimental system that permits physical monitoring of intramolecular recombination by linear substrates released by in vivo restriction from infecting chimera phage. Recombination of the released substrates depended on recA, recBCD and cis-acting Chi octamers. Recombination proficiency was lowered by a xonA mutation and by mutations that inactivated the RuvABC and RecG resolution enzymes. Activity of Chi sites was influenced by their locations and by the number of Chi octamers at each site. A single Chi site stimulated recombination, but a combination of Chi sites on the two homologs was synergistic. These data suggest a role for Chi at both ends of the linear substrate. Chi was lost in all recombinational exchanges stimulated by a single Chi site. Exchanges in substrates with Chi sites on both homologs occurred in the interval between the sites as well as in the flanking interval. These observations suggest that the generation of circular products by intramolecular recombination involves Chi-dependent processing of one end by RecBCD and pairing of the processed end with its duplex homolog.

This article has been cited by other articles:

				C. F. Weil Finding the crosswalks on DNA PNAS, April 30, 2002; 99(9): 5763 - 5765. [Full Text] [PDF]

				Z.-C. Tu, K. C. Ray, S. A. Thompson, and M. J. Blaser Campylobacter fetus Uses Multiple Loci for DNA Inversion within the 5' Conserved Regions of sap Homologs J. Bacteriol., November 15, 2001; 183(22): 6654 - 6661. [Abstract] [Full Text] [PDF]

				M. Bzymek and S. T. Lovett Evidence for Two Mechanisms of Palindrome-Stimulated Deletion in Escherichia coli: Single-Strand Annealing and Replication Slipped Mispairing Genetics, June 1, 2001; 158(2): 527 - 540. [Abstract] [Full Text] [PDF]

				R. Friedman-Ohana, I. Karunker, and A. Cohen A RecG-Independent Nonconservative Branch Migration Mechanism in Escherichia coli Recombination J. Bacteriol., December 1, 1999; 181(23): 7199 - 7205. [Abstract] [Full Text]

				S. D. Reid, R. K. Selander, and T. S. Whittam Sequence Diversity of Flagellin (fliC) Alleles in Pathogenic Escherichia coli J. Bacteriol., January 1, 1999; 181(1): 153 - 160. [Abstract] [Full Text]

				R. Friedman-Ohana and A. Cohen Heteroduplex joint formation in Escherichia coli recombination is initiated by pairing of a 3'-ending strand PNAS, June 9, 1998; 95(12): 6909 - 6914. [Abstract] [Full Text] [PDF]