Abstract
Mitotic checkpoints restrain the onset of mitosis (M) when DNA is incompletely replicated or damaged. These checkpoints are conserved between the fission yeast Schizosaccharomyces pombe and mammals. In both types of organisms, the methylxanthine caffeine overrides the synthesis (S)-M checkpoint that couples mitosis to completion of DNA S phase. The molecular target of caffeine was sought in fission yeast. Caffeine prevented activation of Cds1 and phosphorylation of Chk1, two protein kinases that enforce the S-M checkpoint triggered by hydroxyurea. Caffeine did not inhibit these kinases in vitro but did inhibit Rad3, a kinase that regulates Cds1 and Chk1. In accordance with this finding, caffeine also overrode the G(2)-M DNA damage checkpoint that requires Rad3 function. Rad3 coprecipitated with Cds1 expressed at endogenous amounts, a finding that supports the hypothesis that Rad3 is involved in direct activation of Cds1.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Caffeine / pharmacology*
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Checkpoint Kinase 1
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Checkpoint Kinase 2
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DNA Damage / drug effects
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DNA Replication / drug effects
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DNA-Binding Proteins*
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Endonucleases / genetics
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Endonucleases / metabolism
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Mitosis / drug effects*
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Mitosis / genetics*
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Phosphodiesterase Inhibitors / pharmacology*
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Protein Kinases / genetics
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Protein Kinases / metabolism
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Protein Serine-Threonine Kinases*
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Schizosaccharomyces / cytology
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Schizosaccharomyces / genetics*
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Schizosaccharomyces / metabolism
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Schizosaccharomyces pombe Proteins
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Signal Transduction / drug effects*
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Signal Transduction / genetics
Substances
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DNA-Binding Proteins
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Phosphodiesterase Inhibitors
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Schizosaccharomyces pombe Proteins
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Caffeine
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Protein Kinases
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Checkpoint Kinase 2
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Cds1 protein, S pombe
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Checkpoint Kinase 1
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Chk1 protein, S pombe
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Protein Serine-Threonine Kinases
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Endonucleases
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rad1 protein, S pombe