Threonine-11, Phosphorylated by Rad3 and ATM In Vitro, Is Required for Activation of Fission Yeast Checkpoint Kinase Cds1

Abstract

Fission yeast Cds1 is phosphorylated and activated when DNA replication is interrupted by nucleotide starvation or DNA damage. Cds1 enforces the S-M checkpoint that couples mitosis (M) to the completion of DNA synthesis (S). Cds1 also controls replicational stress tolerance mechanisms. Cds1 is regulated by a group of proteins that includes Rad3, a kinase related to human checkpoint kinase ATM (ataxia telangiectasia mutated). ATM phosphorylates serine or threonine followed by glutamine (SQ or TQ). Here we show that in vitro, Rad3 and ATM phosphorylate the N-terminal domain of Cds1 at the motif T₁₁Q₁₂. Substitution of threonine-11 with alanine (T11A) abolished Cds1 activation that occurs when DNA replication is inhibited by hydroxyurea (HU) treatment. Thecds1-T11A mutant was profoundly sensitive to HU, although not quite as sensitive as a cds1⁻ null mutant. Cds1^T11A was unable to enforce the S-M checkpoint. These results strongly suggest that Rad3-dependent phosphorylation of Cds1 at threonine-11 is required for Cds1 activation and function.

View correction statement:

Threonine-11, Phosphorylated by Rad3 and ATM In Vitro, Is Required for Activation of Fission Yeast Checkpoint Kinase Cds1

ACKNOWLEDGMENTS

We are grateful to Teresa Wang for the gift of anti-Cds1 antibody, H. Murakami and H. Okayama for the gift of plasmid pAL-cds1 and the cds1::ura4strain, and Beth Baber-Furnari for plasmid pREP1-GST-Rad3. Antonia Lopez-Girona made helpful comments and suggestions. Members of the Scripps Cell Cycle Groups provided support and encouragement.

K.T. was supported by The Naito Foundation. This work was funded by NIH grants awarded to C.H.G. and P.R.