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Open AccessJournal ArticleDOI

Chk1 is an essential kinase that is regulated by Atr and required for the G2/M DNA damage checkpoint

TLDR
It is shown that in human cells, Chk1 is phosphorylated on serine 345 (S345) in response to UV, IR, and hydroxyurea (HU).
Abstract
Chk1, an evolutionarily conserved protein kinase, has been implicated in cell cycle checkpoint control in lower eukaryotes. By gene disruption, we show that CHK1 deficiency results in a severe proliferation defect and death in embryonic stem (ES) cells, and peri-implantation embryonic lethality in mice. Through analysis of a conditional CHK1-deficient cell line, we demonstrate that ES cells lacking Chk1 have a defective G(2)/M DNA damage checkpoint in response to gamma-irradiation (IR). CHK1 heterozygosity modestly enhances the tumorigenesis phenotype of WNT-1 transgenic mice. We show that in human cells, Chk1 is phosphorylated on serine 345 (S345) in response to UV, IR, and hydroxyurea (HU). Overexpression of wild-type Atr enhances, whereas overexpression of the kinase-defective mutant Atr inhibits S345 phosphorylation of Chk1 induced by UV treatment. Taken together, these data indicate that Chk1 plays an essential role in the mammalian DNA damage checkpoint, embryonic development, and tumor suppression, and that Atr regulates Chk1.

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Cellular processing of platinum anticancer drugs.

TL;DR: This review focuses on recently discovered cellular pathways that are activated in response to cisplatin, including those involved in regulating drug uptake, the signalling of DNA damage, cell-cycle checkpoints and arrest, DNA repair and cell death.
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The DNA damage response: putting checkpoints in perspective

TL;DR: The inability to repair DNA damage properly in mammals leads to various disorders and enhanced rates of tumour development, and this work has shown that direct activation of DNA repair networks is needed to correct this problem.
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Cell-cycle checkpoints and cancer

TL;DR: All life on earth must cope with constant exposure to DNA-damaging agents such as the Sun's radiation, and how cells respond to DNA damage are critical determinants of whether that individual will develop cancer.
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Sensing DNA Damage Through ATRIP Recognition of RPA-ssDNA Complexes

TL;DR: The data suggest that RPA-coated ssDNA is the critical structure at sites of DNA damage that recruits the ATR-ATRIP complex and facilitates its recognition of substrates for phosphorylation and the initiation of checkpoint signaling.
Journal ArticleDOI

DNA double-strand breaks: signaling, repair and the cancer connection.

TL;DR: Recent progress is described in understanding of how cells detect and signal the presence and repair of one particularly important form of DNA damage induced by ionizing radiation—the DNA double-strand break (DSB).
References
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Journal ArticleDOI

Mice deficient for p53 are developmentally normal but susceptible to spontaneous tumours

TL;DR: Observations indicate that a normal p53 gene is dispensable for embryonic development, that its absence predisposes the animal to neoplastic disease, and that an oncogenic mutant form of p53 is not obligatory for the genesis of many types of tumours.
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A mammalian cell cycle checkpoint pathway utilizing p53 and GADD45 is defective in ataxia-telangiectasia

TL;DR: Three participants are identified (AT gene(s), p53, and GADD45) in a signal transduction pathway that controls cell cycle arrest following DNA damage; abnormalities in this pathway probably contribute to tumor development.
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Requirement for p53 and p21 to Sustain G2 Arrest After DNA Damage

TL;DR: After DNA damage, many cells appear to enter a sustained arrest in the G2 phase of the cell cycle but this arrest could be sustained only when p53 was present in the cell and capable of transcriptionally activating the cyclin-dependent kinase inhibitor p21.
Journal ArticleDOI

Cell Cycle Checkpoints: Preventing an Identity Crisis

TL;DR: Signal transduction pathways that transmit checkpoint signals in response to DNA damage, replication blocks, and spindle damage are revealed, underscoring the conservation of cell cycle regulatory machinery.
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