Role of the Escherichia coli RecQ DNA helicase in SOS signaling and genome stabilization at stalled replication forks

  1. Takashi Hishida1,5,7,
  2. Yong-Woon Han1,5,6,
  3. Tatsuya Shibata1,
  4. Yoshino Kubota1,
  5. Yoshizumi Ishino3,
  6. Hiroshi Iwasaki4, and
  7. Hideo Shinagawa1,2,8
  1. 1Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; 2CREST, Japan Science and Technology Agency, Osaka 565-0871, Japan; 3Department of Genetic Resources Technology, Faculty of Agriculture, Kyushu University, Fukuoka, 812-8581, Japan; 4Graduate School of Integrated Science, Yokohama City University, Yokohama, 230-0045 Japan

Abstract

The RecQ protein family is a highly conserved group of DNA helicases that play roles in maintaining genomic stability. In this study, we present biochemical and genetic evidence that Escherichia coli RecQ processes stalled replication forks and participates in SOS signaling. Cells that carry dnaE486, a mutation in the DNA polymerase III α-catalytic subunit, induce an RecA-dependent SOS response and become highly filamented at the semirestrictive temperature (38°C). An recQ mutation suppresses the induction of SOS response and the filamentation in the dnaE486 mutant at 38°C, causing appearance of a high proportion of anucleate cells. In vitro, RecQ binds and unwinds forked DNA substrates with a gap on the leading strand more efficiently than those with a gap on the lagging strand or Holliday junction DNA. RecQ unwinds the template duplex ahead of the fork, and then the lagging strand is unwound. Consequently, this process generates a single-stranded DNA (ssDNA) gap on the lagging strand adjacent to a replication fork. These results suggest that RecQ functions to generate an initiating signal that can recruit RecA for SOS induction and recombination at stalled replication forks, which are required for the cell cycle checkpoint and resumption of DNA replication.

Keywords

Footnotes

  • Supplemental material is available at http://www.genesdev.org.

  • Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.1223804.

  • 5 These authors contributed equally to this work.

  • Corresponding authors.

  • 7 E-MAIL hishida{at}biken.osaka-u.ac.jp; FAX 81-6-6879-8320

  • 8 E-MAIL shinagaw{at}biken.osaka-u.ac.jp; FAX 81-6-6879-8320.

  • 6 Present address: The Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan.

    • Accepted June 7, 2004.
    • Received May 19, 2004.
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