S-phase-specific activation of Cds1 kinase defines a subpathway of the checkpoint response in Schizosaccharomyces pombe
- Howard D. Lindsay,
- Dominic J.F. Griffiths,
- Rhian J. Edwards,
- Per U. Christensen,
- Johanne M. Murray,
- Fekret Osman,
- Nancy Walworth, and
- Antony M. Carr
- Medical Research Council (MRC) Cell Mutation Unit, Sussex University, Falmer, Sussex BN1 9RR, UK; School of Biological Sciences, Sussex University, Falmer BN1 9SQ, UK; Department of Biochemistry Oxford University, Oxford OX1 3QU, UK; University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854-5635 USA
Abstract
Checkpoints that respond to DNA structure changes were originally defined by the inability of yeast mutants to prevent mitosis following DNA damage or S-phase arrest. Genetic analysis has subsequently identified subpathways of the DNA structure checkpoints, including the reversible arrest of DNA synthesis. Here, we show that the Cds1 kinase is required to slow S phase in the presence of DNA-damaging agents. Cds1 is phosphorylated and activated by S-phase arrest and activated by DNA damage during S phase, but not during G1 or G2. Activation of Cds1 during S phase is dependent on all six checkpoint Rad proteins, and Cds1 interacts both genetically and physically with Rad26. Unlike its Saccharomyces cerevisiae counterpart Rad53, Cds1 is not required for the mitotic arrest checkpoints and, thus, defines an S-phase specific subpathway of the checkpoint response. We propose a model for the DNA structure checkpoints that offers a new perspective on the function of the DNA structure checkpoint proteins. This model suggests that an intrinsic mechanism linking S phase and mitosis may function independently of the known checkpoint proteins.
