Essential and dispensable roles of ATR in cell cycle arrest and genome maintenance.
A Cre/lox-conditional mouse line was generated to evaluate the role of ATR in checkpoint responses to ionizing radiation (IR) and stalled DNA replication. We demonstrate that after IR treatment, ATR and ATM each contribute to early delay in M-phase entry but that ATR regulates a majority of the late phase (2-9 h post-IR). Double deletion of ATR and ATM eliminates nearly all IR-induced delay, indicating that ATR and ATM cooperate in the IR-induced G2/M-phase checkpoint. In contrast to the IR-induced checkpoint, checkpoint delay in response to stalled DNA replication is intact in ATR knockout cells and ATR/ATM and ATR/p53 double-knockout cells. The DNA replication checkpoint remains intact in ATR knockout cells even though the checkpoint-stimulated inhibitory phosphorylation of Cdc2 on T14/Y15 and activating phosphorylation of the Chk1 kinase no longer occur. Thus, incomplete DNA replication in mammalian cells can prevent M-phase entry independently of ATR and inhibitory phosphorylation of Cdc2. When DNA replication inhibitors are removed, ATR knockout cells proceed to mitosis but do so with chromosome breaks, indicating that ATR provides a key genome maintenance function in S phase.
Brown
Eric J
EJ
California Institute of Technology, Pasadena, California 91125, USA. ejbrown@caltech.edu
Baltimore
David
D
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage / Q000502:physiology; D004268:DNA-Binding Proteins; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D011839:Radiation, Ionizing; D025521:Tumor Suppressor Proteins; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D014764:Viral Proteins; D011494:Protein Kinases; C576897:Atr protein, mouse; D064447:Checkpoint Kinase 2; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; C045073:Cre recombinase; D019426:Integrases