The ATM-Chk2-Cdc25A checkpoint pathway guards against radioresistant DNA synthesis

TY - JOUR

T1 - The ATM-Chk2-Cdc25A checkpoint pathway guards against radioresistant DNA synthesis

AU - Falck, J

AU - Mailand, Niels

AU - Syljuåsen, R G

AU - Bartek, J

AU - Lukas, J

PY - 2001/4/12

Y1 - 2001/4/12

N2 - When exposed to ionizing radiation (IR), eukaryotic cells activate checkpoint pathways to delay the progression of the cell cycle. Defects in the IR-induced S-phase checkpoint cause 'radioresistant DNA synthesis', a phenomenon that has been identified in cancer-prone patients suffering from ataxia-telangiectasia, a disease caused by mutations in the ATM gene. The Cdc25A phosphatase activates the cyclin-dependent kinase 2 (Cdk2) needed for DNA synthesis, but becomes degraded in response to DNA damage or stalled replication. Here we report a functional link between ATM, the checkpoint signalling kinase Chk2/Cds1 (Chk2) and Cdc25A, and implicate this mechanism in controlling the S-phase checkpoint. We show that IR-induced destruction of Cdc25A requires both ATM and the Chk2-mediated phosphorylation of Cdc25A on serine 123. An IR-induced loss of Cdc25A protein prevents dephosphorylation of Cdk2 and leads to a transient blockade of DNA replication. We also show that tumour-associated Chk2 alleles cannot bind or phosphorylate Cdc25A, and that cells expressing these Chk2 alleles, elevated Cdc25A or a Cdk2 mutant unable to undergo inhibitory phosphorylation (Cdk2AF) fail to inhibit DNA synthesis when irradiated. These results support Chk2 as a candidate tumour suppressor, and identify the ATM-Chk2-Cdc25A-Cdk2 pathway as a genomic integrity checkpoint that prevents radioresistant DNA synthesis.

AB - When exposed to ionizing radiation (IR), eukaryotic cells activate checkpoint pathways to delay the progression of the cell cycle. Defects in the IR-induced S-phase checkpoint cause 'radioresistant DNA synthesis', a phenomenon that has been identified in cancer-prone patients suffering from ataxia-telangiectasia, a disease caused by mutations in the ATM gene. The Cdc25A phosphatase activates the cyclin-dependent kinase 2 (Cdk2) needed for DNA synthesis, but becomes degraded in response to DNA damage or stalled replication. Here we report a functional link between ATM, the checkpoint signalling kinase Chk2/Cds1 (Chk2) and Cdc25A, and implicate this mechanism in controlling the S-phase checkpoint. We show that IR-induced destruction of Cdc25A requires both ATM and the Chk2-mediated phosphorylation of Cdc25A on serine 123. An IR-induced loss of Cdc25A protein prevents dephosphorylation of Cdk2 and leads to a transient blockade of DNA replication. We also show that tumour-associated Chk2 alleles cannot bind or phosphorylate Cdc25A, and that cells expressing these Chk2 alleles, elevated Cdc25A or a Cdk2 mutant unable to undergo inhibitory phosphorylation (Cdk2AF) fail to inhibit DNA synthesis when irradiated. These results support Chk2 as a candidate tumour suppressor, and identify the ATM-Chk2-Cdc25A-Cdk2 pathway as a genomic integrity checkpoint that prevents radioresistant DNA synthesis.

KW - Alleles

KW - Animals

KW - Ataxia Telangiectasia Mutated Proteins

KW - Cell Cycle

KW - Cell Cycle Proteins

KW - Cell Line

KW - Checkpoint Kinase 2

KW - DNA Replication

KW - DNA-Binding Proteins

KW - Humans

KW - Mice

KW - Phosphorylation

KW - Protein Kinases

KW - Protein-Serine-Threonine Kinases

KW - Radiation Tolerance

KW - Radiation, Ionizing

KW - S Phase

KW - Serine

KW - Signal Transduction

KW - Transfection

KW - Tumor Suppressor Proteins

KW - cdc25 Phosphatases

U2 - 10.1038/35071124

DO - 10.1038/35071124

M3 - Journal article

C2 - 11298456

SN - 0028-0836

VL - 410

SP - 842

EP - 847

JO - Nature

JF - Nature

IS - 6830

ER -