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G(1)/S and G(2)/M cyclin-dependent kinase activities commit cells to death in the absence of the S-phase checkpoint

Nicola Manfrini1, Elisa Gobbini, Veronica Baldo

  • 1Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy.

Molecular and Cellular Biology
|October 10, 2012
PubMed

Insights

Mec1 and Rad53 kinases are vital for yeast cell survival and DNA replication. Lowering Cdk1 activity rescues mec1 and rad53 mutants, revealing cell cycle control

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Mec1 and Rad53 protein kinases are essential for budding yeast viability.
  • These kinases activate the S-phase checkpoint, crucial for DNA replication under stress.
  • The relationship between Mec1/Rad53's essential functions and their role in the S-phase checkpoint is unclear.

Purpose of the Study:

  • To investigate the connection between Mec1/Rad53's essential functions and their role in supporting DNA replication under stress.
  • To elucidate the nature of replication stress-dependent lethality in mec1 and rad53 mutants.

Main Methods:

  • Studied the effects of decreasing cyclin-dependent kinase 1 (Cdk1) activity on mec1 and rad53 mutants.
  • Assessed survival rates of mutants under replication stress (hydroxyurea) and unperturbed conditions.
  • Investigated the roles of Cdk1 in G1 and mitosis, and the impact of delaying cell cycle transitions (G1/S, spindle elongation).

Main Results:

  • Reduced Cdk1 activity alleviated the lethal effects of mec1 and rad53 mutations, irrespective of replication stress.
  • Lethality in mec1 and rad53 mutants involves Cdk1 functions in both G1 and mitosis.
  • Delaying the G1/S transition or spindle elongation rescued mec1 and rad53 mutants, both with and without replication stress.

Conclusions:

  • Inappropriate entry into S phase and segregation of incompletely replicated chromosomes contribute to cell death when the S-phase checkpoint is non-functional.
  • The essential functions of Mec1 and Rad53 are likely intertwined with their roles in supporting DNA synthesis under stress.
  • Cell cycle control by Cdk1 plays a critical role in the lethality observed in Mec1 and Rad53 deficient cells.

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