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Mrc1 is a replication fork component whose phosphorylation in response to DNA replication stress activates Rad53

Alexander J Osborn1, Stephen J Elledge

  • 1Verna and Marrs MacLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.

Genes & Development
|July 17, 2003
PubMed

Insights

The Mediator protein Mrc1 stabilizes stalled DNA replication forks in budding yeast. Mec1 kinase phosphorylates Mrc1 at stalled forks, activating the Rad53 checkpoint for DNA repair.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • DNA replication requires stable forks for timely synthesis.
  • Cellular checkpoints maintain genomic integrity during replication stress.
  • Mec1 and Rad53 kinases are key components of the DNA replication checkpoint.

Purpose of the Study:

  • To investigate the role of the Mediator protein Mrc1 in DNA replication and checkpoint activation.
  • To elucidate the mechanism by which Mrc1 interacts with Mec1 and Rad53 kinases.
  • To understand how Mrc1 contributes to the stability of stalled replication forks.

Main Methods:

  • Chromatin immunoprecipitation to track Mrc1 localization.
  • Analysis of Mrc1 phosphorylation mutants.
  • Assessment of DNA replication and checkpoint activation in budding yeast.

Main Results:

  • Mrc1 localizes to replication forks and moves with them.
  • Mec1 kinase is recruited to stalled replication sites and phosphorylates Mrc1.
  • Mutation of Mec1 phosphorylation sites on Mrc1 abolishes Rad53 activation without affecting DNA replication.

Conclusions:

  • Mrc1 acts as a scaffold at replication forks, facilitating Mec1 recruitment and Rad53 activation.
  • Mec1-mediated phosphorylation of Mrc1 is crucial for initiating the DNA replication checkpoint.
  • This mechanism ensures the stability of stalled forks and promotes DNA synthesis resumption.

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