Cleavage of claspin by caspase-7 during apoptosis inhibits the Chk1 pathway.
Claspin is required for the phosphorylation and activation of the Chk1 protein kinase by ATR during DNA replication and in response to DNA damage. This checkpoint pathway plays a critical role in the resistance of cells to genotoxic stress. Here, we show that human Claspin is cleaved by caspase-7 during the initiation of apoptosis. In cells, induction of DNA damage by etoposide at first produced rapid phosphorylation of Chk1 at a site targeted by ATR. Subsequently, etoposide caused activation of caspase-7, cleavage of Claspin, and dephosphorylation of Chk1. In apoptotic cell extracts, Claspin was cleaved by caspase-7 at a single aspartate residue into a large N-terminal fragment and a smaller C-terminal fragment that contain different functional domains. The large N-terminal fragment was heavily phosphorylated in a human cell-free system in response to double-stranded DNA oligonucleotides, and this fragment retained Chk1 binding activity. In contrast, the smaller C-terminal fragment did not bind Chk1, but did associate with DNA and inhibited the DNA-dependent phosphorylation of Chk1 associated with its activation. These results indicate that cleavage of Claspin by caspase-7 inactivates the Chk1 signaling pathway. This mechanism may regulate the balance between cell cycle arrest and induction of apoptosis during the response to genotoxic stress.
Clarke
Catriona A L
CA
Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom.
Bennett
Lara N
LN
Clarke
Paul R
PR
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001224:Aspartic Acid / Q000737:chemistry; D001665:Binding Sites; D053179:Caspase 7; D020169:Caspases / Q000737:chemistry / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D000071877:Checkpoint Kinase 1; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004261:DNA Replication; D004305:Dose-Response Relationship, Drug; D004330:Drosophila; D005047:Etoposide / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D014981:Xenopus; D029867:Xenopus Proteins
D048868:Adaptor Proteins, Signal Transducing; C488158:CLSPN protein, human; D009841:Oligonucleotides; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D001224:Aspartic Acid; D005047:Etoposide; D004247:DNA; D003513:Cycloheximide; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; C000605869:Chek1 protein, mouse; C505520:CASP7 protein, human; C505524:Casp7 protein, mouse; D053179:Caspase 7; D020169:Caspases