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Mrc1 phosphorylation in response to DNA replication stress is required for Mec1 accumulation at the stalled fork

Maria L Naylor1, Ju-mei Li, Alex J Osborn

  • 1Department of Genetics, Harvard Medical School, Division of Genetics, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA.

Proceedings of the National Academy of Sciences of the United States of America
|June 12, 2009
PubMed

Insights

DNA replication stress triggers a pathway involving Mec1 sensor kinase and Mrc1 mediator. Mec1-dependent Mrc1 phosphorylation creates a feedback loop stabilizing the replication machinery at stalled forks.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • DNA Replication and Repair

Background:

  • DNA replication stress activates crucial cellular responses to maintain genome stability.
  • The Mec1 (DNA damage checkpoint kinase 1) sensor kinase, Mrc1 (mediator of replication checkpoint) mediator, and Rad53 effector kinase are key components of the S-phase checkpoint.
  • Stabilizing stalled replication forks is essential for preventing genomic instability.

Purpose of the Study:

  • To investigate the role of Mrc1 phosphorylation in the DNA replication stress response.
  • To elucidate the mechanism by which Mrc1 facilitates checkpoint signal amplification.
  • To understand the structure-function relationship of Mrc1 in mediating replication fork stability.

Main Methods:

  • Utilizing budding yeast as a model organism.
  • Employing genetic and biochemical approaches, including structure-function analysis of Mrc1.
  • Investigating Mec1-dependent and Rad53-independent phosphorylation events.

Main Results:

  • Mec1-dependent, Rad53-independent phosphorylation of Mrc1 is critical for establishing a positive feedback loop.
  • This feedback loop stabilizes Mec1 and the replisome at stalled replication forks.
  • A central region of Mrc1 was identified as essential for its mediator function and interaction with replisome components.

Conclusions:

  • Mrc1 phosphorylation by Mec1 is a key regulatory event in the replication stress response.
  • Mrc1 acts as a crucial mediator, amplifying checkpoint signals and stabilizing stalled forks.
  • These findings provide new insights into the intricate mechanisms governing DNA replication fidelity.

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