Serine-345 is required for Rad3-dependent phosphorylation and function of checkpoint kinase Chk1 in fission yeast
- Antonia Lopez-Girona,
- Katsunori Tanaka,
- Xiao-Bo Chen,
- Beth A. Baber,
- Clare H. McGowan, and
- Paul Russell*
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Edited by Tony Hunter, The Salk Institute for Biological Studies, La Jolla, CA, and approved July 24, 2001 (received for review November 27, 2000)
Abstract
Genome integrity is monitored by a checkpoint that delays mitosis in response to DNA damage. This checkpoint is enforced by Chk1, a protein kinase that inhibits the mitotic inducer Cdc25. In fission yeast, Chk1 is regulated by a group of proteins that includes Rad3, a protein kinase related to human ATM and ATR. These kinases phosphorylate serine or threonine followed by glutamine (SQ/TQ). Fission yeast and human Chk1 proteins share two conserved SQ motifs at serine-345 and serine-367. Serine-345 of human Chk1 is phosphorylated in response to DNA damage. Here we report that Rad3 and ATM phosphorylate serine-345 of fission yeast Chk1. Mutation of serine-345 (chk1-S345A) abrogates Rad3-dependent phosphorylation of Chk1 in vivo. The chk1-S345A cells are sensitive to DNA damage and are checkpoint defective. In contrast, mutations of serine-367 and other SQ/TQ sites do not substantially impair the checkpoint or cause damage sensitivity. These findings attest to the importance of serine-345 phosphorylation for Chk1 function and strengthen evidence that transduction of the DNA damage checkpoint signal requires direct phosphorylation of Chk1 by Rad3.
Footnotes
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↵ * To whom reprint requests should be addressed at: The Scripps Research Institute, MB3, 10550 North Torrey Pines Road, La Jolla, CA 92037. E-mail: prussell{at}scripps.edu.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviations:
- GST,
- glutathione S-transferase;
- M,
- mitosis
- Copyright © 2001, The National Academy of Sciences
