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Nature 424, 1078-1083 (28 August 2003) | doi:10.1038/nature01900; Received 4 May 2003; Accepted 4 July 2003

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S-phase checkpoint proteins Tof1 and Mrc1 form a stable replication-pausing complex

Yuki Katou1,2, Yutaka Kanoh1,2, Masashige Bando1, Hideki Noguchi1, Hirokazu Tanaka1,3, Toshihiko Ashikari4, Katsunori Sugimoto5 & Katsuhiko Shirahige1

  1. Genome Structure and Function Team, Human Genome Research Group, RIKEN Genomic Science Center, 1-7-22 Suehiro-cho, and
  2. Science of Biological Supramolecular Systems, Graduate School of Integrated Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
  3. Division of Biochemistry, Kihara Institute for Biological Research and Graduate School of Integrated Science, Yokohama City University, 641-12, Maioka-cho, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
  4. Institute for Advanced Technology, Suntory Limited, 1-1-1, Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka, 618-8503, Japan
  5. Division of Biological Science, Nagoya University Graduate School of Science, Nagoya, 464-0814, Japan

Correspondence to: Katsuhiko Shirahige1 Correspondence and requests for materials should be addressed to K.S. (Email: shirahi@gsc.riken.go.jp). Data presented in this paper can be obtained from GEO (http://www.ncbi.nlm.nih.gov/geo) with accession number GSE486.

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The checkpoint regulatory mechanism has an important role in maintaining the integrity of the genome1, 2, 3, 4, 5. This is particularly important in S phase of the cell cycle, when genomic DNA is most susceptible to various environmental hazards3, 6, 7. When chemical agents damage DNA, activation of checkpoint signalling pathways results in a temporary cessation of DNA replication. A replication-pausing complex is believed to be created at the arrested forks to activate further checkpoint cascades, leading to repair of the damaged DNA. Thus, checkpoint factors are thought to act not only to arrest replication but also to maintain a stable replication complex at replication forks6, 7, 8, 9. However, the molecular mechanism coupling checkpoint regulation and replication arrest is unknown. Here we demonstrate that the checkpoint regulatory proteins Tof1 and Mrc1 interact directly with the DNA replication machinery in Saccharomyces cerevisiae. When hydroxyurea blocks chromosomal replication, this assembly forms a stable pausing structure that serves to anchor subsequent DNA repair events.