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  1. Article ; Online: BRCA1-dependent Chk1 phosphorylation triggers partial chromatin disassociation of phosphorylated Chk1 and facilitates S-phase cell cycle arrest.

    Yarden, Ronit I / Metsuyanim, Sally / Pickholtz, Itay / Shabbeer, Shabana / Tellio, Hadass / Papa, Moshe Z

    The international journal of biochemistry & cell biology

    2012  Volume 44, Issue 11, Page(s) 1761–1769

    Abstract: Chk1 phosphorylation by the PI3-like kinases ATR and ATM is critical for its activation and its role in prevention of premature mitotic entry in response to DNA damage or stalled replication. The breast and ovarian tumor suppressor, BRCA1, is among ... ...

    Abstract Chk1 phosphorylation by the PI3-like kinases ATR and ATM is critical for its activation and its role in prevention of premature mitotic entry in response to DNA damage or stalled replication. The breast and ovarian tumor suppressor, BRCA1, is among several checkpoint mediators that are required for Chk1 activation by ATM and ATR. Previously we showed that BRCA1 is necessary for Chk1 phosphorylation and activation following ionizing radiation. BRCA1 has been implicated in S-phase checkpoint control yet its mechanism of action is not well characterized. Here we report that BRCA1 is critical for Chk1 phosphorylation in response to inhibition of replication by either cisplatin or hydroxyurea. While Chk1 phosphorylation of S317 is fully dependent on BRCA1, additional proteins may mediate S345 phosphorylation at later time points. In addition, we show that a subset of phosphorylated Chk1 is released from the chromatin in a BRCA1-dependent manner which may lead to the phosphorylation of Chk1 substrate, Cdc25C, on S216 and to S-phase checkpoint activation. Inhibition of Chk1 kinase by UCN-01 or expression of Chk1 phosphorylation mutants in which the serine residues were substituted with alanine residues abrogates BRCA1-dependent cell cycle arrest in response replication inhibition. These data reveal that BRCA1 facilitates Chk1 phosphorylation and its partial chromatin dissociation following replication inhibition that is likely to be required for S-phase checkpoint signaling.
    MeSH term(s) BRCA1 Protein/metabolism ; Cell Cycle Checkpoints/drug effects ; Cell Cycle Checkpoints/radiation effects ; Cell Line, Tumor ; Checkpoint Kinase 1 ; Chromatin/drug effects ; Chromatin/metabolism ; DNA Damage ; DNA Replication/drug effects ; DNA Replication/radiation effects ; Enzyme Activation/drug effects ; Enzyme Activation/radiation effects ; Humans ; Hydroxyurea/pharmacology ; Mutant Proteins/metabolism ; Phosphorylation/drug effects ; Phosphorylation/radiation effects ; Phosphoserine/metabolism ; Protein Kinases/metabolism ; Radiation, Ionizing ; S Phase/drug effects ; S Phase/radiation effects ; Signal Transduction/drug effects ; Signal Transduction/radiation effects ; Stress, Physiological/drug effects ; Stress, Physiological/radiation effects
    Chemical Substances BRCA1 Protein ; Chromatin ; Mutant Proteins ; Phosphoserine (17885-08-4) ; Protein Kinases (EC 2.7.-) ; CHEK1 protein, human (EC 2.7.11.1) ; Checkpoint Kinase 1 (EC 2.7.11.1) ; Hydroxyurea (X6Q56QN5QC)
    Language English
    Publishing date 2012-06-26
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1228429-4
    ISSN 1878-5875 ; 1357-2725
    ISSN (online) 1878-5875
    ISSN 1357-2725
    DOI 10.1016/j.biocel.2012.06.026
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: BRCA1-dependent Chk1 phosphorylation triggers partial chromatin disassociation of phosphorylated Chk1 and facilitates S-phase cell cycle arrest

    Yarden, Ronit I. / Metsuyanim, Sally / Pickholtz, Itay / Shabbeer, Shabana / Tellio, Hadass / Papa, Moshe Z.

    international journal of biochemistry & cell biology

    Volume v. 44,, Issue no. 1

    Abstract: Chk1 phosphorylation by the PI3-like kinases ATR and ATM is critical for its activation and its role in prevention of premature mitotic entry in response to DNA damage or stalled replication. The breast and ovarian tumor suppressor, BRCA1, is among ... ...

    Abstract Chk1 phosphorylation by the PI3-like kinases ATR and ATM is critical for its activation and its role in prevention of premature mitotic entry in response to DNA damage or stalled replication. The breast and ovarian tumor suppressor, BRCA1, is among several checkpoint mediators that are required for Chk1 activation by ATM and ATR. Previously we showed that BRCA1 is necessary for Chk1 phosphorylation and activation following ionizing radiation. BRCA1 has been implicated in S-phase checkpoint control yet its mechanism of action is not well characterized. Here we report that BRCA1 is critical for Chk1 phosphorylation in response to inhibition of replication by either cisplatin or hydroxyurea. While Chk1 phosphorylation of S317 is fully dependent on BRCA1, additional proteins may mediate S345 phosphorylation at later time points. In addition, we show that a subset of phosphorylated Chk1 is released from the chromatin in a BRCA1-dependent manner which may lead to the phosphorylation of Chk1 substrate, Cdc25C, on S216 and to S-phase checkpoint activation. Inhibition of Chk1 kinase by UCN-01 or expression of Chk1 phosphorylation mutants in which the serine residues were substituted with alanine residues abrogates BRCA1-dependent cell cycle arrest in response replication inhibition. These data reveal that BRCA1 facilitates Chk1 phosphorylation and its partial chromatin dissociation following replication inhibition that is likely to be required for S-phase checkpoint signaling.
    Keywords dissociation ; phosphotransferases (kinases) ; alanine ; tumor suppressor proteins ; serine ; cell cycle checkpoints ; mutants ; ionizing radiation ; DNA damage ; mechanism of action ; cisplatin ; chromatin ; phosphorylation ; hydroxyurea
    Language English
    Document type Article
    ISSN 1357-2725
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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