Caffeine can override the S-M checkpoint in fission yeast.
The replication checkpoint (or 'S-M checkpoint') control prevents progression into mitosis when DNA replication is incomplete. Caffeine has been known for some time to have the capacity to override the S-M checkpoint in animal cells. We show here that caffeine also disrupts the S-M checkpoint in the fission yeast Schizosaccharomyces pombe. By contrast, no comparable effects of caffeine on the S. pombe DNA damage checkpoint were seen. S. pombe cells arrested in early S phase and then exposed to caffeine lost viability rapidly as they attempted to enter mitosis, which was accompanied by tyrosine dephosphorylation of Cdc2. Despite this, the caffeine-induced loss of viability was not blocked in a temperature-sensitive cdc2 mutant incubated at the restrictive temperature, although catastrophic mitosis was prevented under these conditions. This suggests that, in addition to S-M checkpoint control, a caffeine-sensitive function may be important for maintenance of cell viability during S phase arrest. The lethality of a combination of caffeine with the DNA replication inhibitor hydroxyurea was suppressed by overexpression of Cds1 or Chk1, protein kinases previously implicated in S-M checkpoint control and recovery from S phase arrest. In addition, the same combination of drugs was specifically tolerated in cells overexpressing either of two novel S. pombe genes isolated in a cDNA library screen. These findings should allow further molecular investigation of the regulation of S phase arrest, and may provide a useful system with which to identify novel drugs that specifically abrogate the checkpoint control.
Wang
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SW
Imperial Cancer Research Fund, Cell Regulation Laboratory, PO Box 123, Lincoln's Inn Fields, London WC2 A3P, UK.
Norbury
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Harris
A L
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Toda
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002110:Caffeine / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004352:Drug Resistance, Microbial / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015723:Gene Library; D005838:Genotype; D006918:Hydroxyurea / Q000494:pharmacology; D007700:Kinetics; D008938:Mitosis; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D012264:Ribonucleotide Reductases; D016196:S Phase; D012568:Schizosaccharomyces / Q000166:cytology* / Q000187:drug effects* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins
D005656:Fungal Proteins; D029702:Schizosaccharomyces pombe Proteins; D002110:Caffeine; D012264:Ribonucleotide Reductases; C080927:SUC22 protein, S pombe; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; D006918:Hydroxyurea