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  • The EMBO Journal (2003) 22, 324 - 334
  • doi:10.1093/emboj/cdg027

Hallmarks of homology recognition by RecA-like recombinases are exhibited by the unrelated Escherichia coli RecT protein

Philippe Noirot1, Ravindra C. Gupta2, Charles M. Radding3 and Richard D. Kolodner4

  1. Laboratoire de Génétique Microbienne, INRA, 78352 Jouy en Josas Cedex, France
  2. Department of Biological Sciences, SUNY at Albany, 1400 Washington Avenue, Albany, NY 12222, USA
  3. Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA
  4. Ludwig Institute for Cancer Research, Cancer Center and Department of Medicine, University of California-San Diego School of Medicine, La Jolla, CA 92093, USA

Correspondence to:

Richard D. Kolodner, E-mail: rkolodner@ucsd.edu

Received 31 July 2002; Accepted 21 November 2002; Revised 11 November 2002

Homologous recombination is a fundamental process for genome maintenance and evolution. Various proteins capable of performing homology recognition and pairing of DNA strands have been isolated from many organisms. The RecA family of proteins exhibits a number of biochemical properties that are considered hallmarks of homology recognition. Here, we investigated whether the unrelated Escherichia coli RecT protein, which mediates homologous pairing and strand exchange, also exhibits such properties. We found that, like RecA and known RecA homologs: (i) RecT promotes the co-aggregation of ssDNA with duplex DNA, which is known to facilitate homologous contacts; (ii) RecT binding to ssDNA mediates unstacking of the bases, a key step in homology recognition; (iii) RecT mediates the formation of a three-strand synaptic intermediate where pairing is facilitated by local helix destabilization, and the preferential switching of A:T base pairs mediates recognition of homology; and (iv) RecT-mediated pairing occurs from both 3'- and 5'-single-stranded ends. Taken together, our results show that RecT shares fundamental homology-recognition properties with the RecA homologs, and provide new insights on an underlying universal mechanism of homologous recognition.

  • Keywords:

    • DNA base unstacking,
    • DNA co-aggregation,
    • DNA unwinding,
    • homologous pairing,
    • RecT