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Study of the DNA Damage Checkpoint using Xenopus Egg Extracts
10:55

Study of the DNA Damage Checkpoint using Xenopus Egg Extracts

Published on: November 5, 2012

Mcm2 is a direct substrate of ATM and ATR during DNA damage and DNA replication checkpoint responses

Hae Yong Yoo1, Anna Shevchenko, Andrej Shevchenko

  • 1Division of Biology, 1200 E. California Blvd., California Institute of Technology, Pasadena, CA 91125, USA.

The Journal of Biological Chemistry
|September 28, 2004
PubMed

Insights

ATM and ATR kinases phosphorylate the Mcm2 replication protein, crucial for DNA damage and replication checkpoints in Xenopus egg extracts. This phosphorylation is essential for blocking DNA replication upon damage.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • ATM (Ataxia-telangiectasia mutated) and ATR (Ataxia-telangiectasia and Rad3-related) are vital kinases regulating cellular responses to DNA damage and replication stress in vertebrates.
  • These kinases activate signaling pathways that halt chromosome replication when DNA lesions are present, ensuring genomic stability.

Purpose of the Study:

  • To investigate the role of ATM and ATR in DNA replication checkpoint control in Xenopus egg extracts.
  • To identify and characterize ATM-binding proteins involved in these checkpoint responses.
  • To elucidate the specific phosphorylation events mediated by ATM and ATR on replication proteins.

Main Methods:

  • Isolation of a full-length Xenopus ATM cDNA.
  • Identification of Mcm2 as an ATM-binding protein using specific antibodies in Xenopus egg extracts.
  • Analysis of Mcm2 phosphorylation at Ser(92) in response to DNA damage and replication blocks.
  • Cell-free kinase assays to determine direct phosphorylation of Mcm2 by ATM and ATR.
  • Immunodepletion experiments to assess the necessity of ATM and ATR for checkpoint activation.

Main Results:

  • Xenopus Mcm2 was identified as an ATM-binding protein.
  • Mcm2 phosphorylation at Ser(92) was observed in response to double-stranded DNA breaks and replication blocks.
  • Both ATM and ATR kinases directly phosphorylated Mcm2 at Ser(92), with relative contributions varying by DNA signal.
  • Depletion of ATM and ATR abolished the DNA replication checkpoint in response to double-stranded DNA breaks.

Conclusions:

  • ATM and ATR are essential for the DNA damage and replication checkpoint responses in Xenopus egg extracts.
  • The functionally critical replication protein Mcm2 is a direct target of ATM and ATR phosphorylation during these checkpoints.
  • Phosphorylation of Mcm2 by ATM and ATR plays a key role in inhibiting chromosomal DNA replication under stress conditions.

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