Dual Regulation of Cdc25A by Chk1 and p53-ATF3 in DNA Replication Checkpoint Control

Abstract

Eukaryotic cells respond to DNA damage and stalled replication forks by activating signaling pathways that promote cell cycle arrest and DNA repair. A systematic screening of the protein kinase small interfering RNA library reveals that Chk1 and ataxia telangiectasia-mutated (ATM) and Rad3-related (ATR) are the main kinases responsible for intra-S-phase checkpoint upon topoisomerase I inhibitor camptothecin-induced DNA damage. It is well known that ATR-Chk1-mediated protein degradation of Cdc25A protein phosphatase is a crucial mechanism conferring this checkpoint activation. Here we describe another mechanism underlying Cdc25A down-regulation in response to DNA damage that occurs at the transcriptional level. We show that activation of tumor suppressor p53 by DNA damage results in inhibition of Cdc25A transcription as a result of activation of transcriptional repressor ATF3 that directly binds to the Cdc25A promoter. In cells deficient in both Chk1 and p53, Cdc25A down-regulation upon camptothecin-induced DNA damage is completely abolished, leading to severe defects in cell cycle checkpoints and remarkable cell death in mitosis. Our findings reveal in in of Cdc25A in DNA damage Chk1 Cdc25A and protein inhibition of Cdc25A transcription by is for the of cell cycle Eukaryotic cells respond to DNA damage and stalled replication forks by activating signaling pathways that promote cell cycle arrest and DNA repair. A systematic screening of the protein kinase small interfering RNA library reveals that Chk1 and ataxia telangiectasia-mutated (ATM) and Rad3-related (ATR) are the main kinases responsible for intra-S-phase checkpoint upon topoisomerase I inhibitor camptothecin-induced DNA damage. It is well known that ATR-Chk1-mediated protein degradation of Cdc25A protein phosphatase is a crucial mechanism conferring this checkpoint activation. Here we describe another mechanism underlying Cdc25A down-regulation in response to DNA damage that occurs at the transcriptional level. We show that activation of tumor suppressor p53 by DNA damage results in inhibition of Cdc25A transcription as a result of activation of transcriptional repressor ATF3 that directly binds to the Cdc25A promoter. In cells deficient in both Chk1 and p53, Cdc25A down-regulation upon camptothecin-induced DNA damage is completely abolished, leading to severe defects in cell cycle checkpoints and remarkable cell death in mitosis. Our findings reveal in in of Cdc25A in DNA damage Chk1 Cdc25A and protein inhibition of Cdc25A transcription by is for the of cell cycle respond to DNA damage by by cell death are that arrest the cell cycle in response to DNA damage is by ataxia telangiectasia-mutated and ataxia activating transcription small interfering cell ataxia telangiectasia-mutated and ataxia activating transcription small interfering cell the DNA and kinases Chk1 and kinases the by the of cell cycle as and leading to of and protein kinases for and DNA Cdc25A by Chk1 the and the leading to inhibition of DNA replication the that is DNA damage and is crucial in of cell cycle and activation of the tumor suppressor p53 is for of cell cycle transcriptional activation of the of p53 in both and checkpoints defects in checkpoint of p53 to checkpoint response and to DNA damage the of cell cycle checkpoint in DNA damage of cell cycle checkpoint to a for In inhibition of cell cycle checkpoint pathways to cells to the mechanism underlying this in cells is completely transcription a of transcriptional is of the of p53 the of the as a transcriptional the and to as transcriptional and and to a DNA in for transcriptional ATF3 is a upon the of cells to a of and as well as as and of cells by DNA damage and by the of cell cycle checkpoint in is a topoisomerase I inhibitor that DNA replication by and DNA and is to In as and are of and for and and is as a to DNA damage we a mechanism of Cdc25A in DNA damage the transcriptional by ATF3 in a this protein Cdc25A down-regulation upon DNA damage is well in the of of this to severe defects in DNA damage cells to DNA and cell Our results the mechanism by inhibition of Chk1 tumor cells to and cell and by in and and at RNA the RNA I and for and for and and for cycle by DNA cells in and and for at in the cells by cells by and by cells to the and by cells in and for in and cells in of and of a at in the cells and by cell cells for and to the by by RNA and library of 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