Claspin operates downstream of TopBP1 to direct ATR signaling towards Chk1 activation
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Claspin operates downstream of TopBP1 to direct ATR signaling towards Chk1 activation. / Liu, Shizhou; Bekker-Jensen, Simon; Mailand, Niels; Lukas, Claudia; Bartek, Jiri; Lukas, Jiri.
In: Molecular and Cellular Biology, Vol. 26, No. 16, 2006, p. 6056-64.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Claspin operates downstream of TopBP1 to direct ATR signaling towards Chk1 activation
AU - Liu, Shizhou
AU - Bekker-Jensen, Simon
AU - Mailand, Niels
AU - Lukas, Claudia
AU - Bartek, Jiri
AU - Lukas, Jiri
PY - 2006
Y1 - 2006
N2 - TopBP1 and Claspin are adaptor proteins that facilitate phosphorylation of Chk1 by the ATR kinase in response to genotoxic stress. Despite their established requirement for Chk1 activation, the exact way in which TopBP1 and Claspin control Chk1 phosphorylation remains unclear. We show that TopBP1 tightly colocalizes with ATR in distinct nuclear subcompartments generated by DNA damage. Although depletion of TopBP1 by RNA interference (RNAi) strongly impaired phosphorylation of multiple ATR targets, including Chk1, Nbs1, Smc1, and H2AX, it did not interfere with ATR assembly at the sites of DNA damage. These findings challenge the current concept of ATR activation by recruitment to damaged DNA. In contrast, Claspin, like Chk1, remained distributed throughout the nucleus both before and after DNA damage. Consistently, the RNAi-mediated ablation of Claspin selectively abrogated ATR's ability to phosphorylate Chk1 but not other ATR targets. In addition, downregulation of Claspin mimicked Chk1 inactivation by inducing spontaneous DNA damage. Finally, we show that TopBP1 is required for the DNA damage-induced interaction between Claspin and Chk1. Together, these results suggest that while TopBP1 is a general regulator of ATR, Claspin operates downstream of TopBP1 to selectively regulate the Chk1-controlled branch of the genotoxic stress response.
AB - TopBP1 and Claspin are adaptor proteins that facilitate phosphorylation of Chk1 by the ATR kinase in response to genotoxic stress. Despite their established requirement for Chk1 activation, the exact way in which TopBP1 and Claspin control Chk1 phosphorylation remains unclear. We show that TopBP1 tightly colocalizes with ATR in distinct nuclear subcompartments generated by DNA damage. Although depletion of TopBP1 by RNA interference (RNAi) strongly impaired phosphorylation of multiple ATR targets, including Chk1, Nbs1, Smc1, and H2AX, it did not interfere with ATR assembly at the sites of DNA damage. These findings challenge the current concept of ATR activation by recruitment to damaged DNA. In contrast, Claspin, like Chk1, remained distributed throughout the nucleus both before and after DNA damage. Consistently, the RNAi-mediated ablation of Claspin selectively abrogated ATR's ability to phosphorylate Chk1 but not other ATR targets. In addition, downregulation of Claspin mimicked Chk1 inactivation by inducing spontaneous DNA damage. Finally, we show that TopBP1 is required for the DNA damage-induced interaction between Claspin and Chk1. Together, these results suggest that while TopBP1 is a general regulator of ATR, Claspin operates downstream of TopBP1 to selectively regulate the Chk1-controlled branch of the genotoxic stress response.
KW - Adaptor Proteins, Signal Transducing
KW - Carrier Proteins
KW - Cell Cycle Proteins
KW - DNA Damage
KW - DNA Replication
KW - DNA-Binding Proteins
KW - Down-Regulation
KW - Enzyme Activation
KW - Humans
KW - Models, Genetic
KW - Nuclear Proteins
KW - Phenotype
KW - Phosphorylation
KW - Protein Binding
KW - Protein Kinases
KW - Protein-Serine-Threonine Kinases
KW - RNA Interference
KW - Signal Transduction
KW - Tumor Cells, Cultured
U2 - 10.1128/MCB.00492-06
DO - 10.1128/MCB.00492-06
M3 - Journal article
C2 - 16880517
VL - 26
SP - 6056
EP - 6064
JO - Molecular and Cellular Biology
JF - Molecular and Cellular Biology
SN - 0270-7306
IS - 16
ER -
ID: 40291287