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Phosphorylation of the MBF repressor Yox1p by the DNA replication checkpoint keeps the G1/S cell-cycle

Catia Caetano1, Steffi Klier, Robertus A M de Bruin

  • 1MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom.

Plos One
|March 2, 2011
PubMed
Abstract

Insights

In fission yeast, Yox1p and Nrm1p repress MBF targets. DNA replication stress triggers Yox1p phosphorylation, causing dissociation from MBF and activating G1/S transcription to maintain genomic stability.

Area of Science:

  • Cell biology
  • Molecular biology
  • Genetics

Background:

  • G1/S cell-cycle transcription in fission yeast relies on MBF.
  • Nrm1p and Yox1p form a negative feedback loop to repress MBF targets as cells exit G1.
  • DNA replication stress leads to sustained expression of MBF-dependent genes.

Purpose of the Study:

  • To investigate the roles of Yox1p and Nrm1p in MBF-dependent transcription.
  • To elucidate the mechanism of MBF target gene de-repression during DNA replication stress.
  • To determine the role of Yox1p phosphorylation in the DNA replication checkpoint response.

Main Methods:

  • Investigated Yox1p and Nrm1p binding to MBF.
  • Analyzed the dissociation of Yox1p and Nrm1p from MBF under DNA replication stress.
  • Identified Cds1p-dependent phosphorylation of Yox1p at specific sites (Ser114, Thr115).

Main Results:

  • Yox1p binding to MBF is dependent on Nrm1p; they require each other for repression.
  • Both Yox1p and Nrm1p dissociate from MBF promoters upon DNA replication stress, leading to de-repression.
  • Phosphorylation of Yox1p at Ser114, Thr115 by Cds1p is crucial for checkpoint-dependent activation of the G1/S transcriptional program.

Conclusions:

  • Checkpoint-dependent phosphorylation of Yox1p at Ser114, Thr115 de-represses the MBF transcriptional program.
  • Remodeling of the cell cycle transcriptional program by the DNA replication checkpoint is vital for preventing genomic instability.

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