A Mec1- and Rad53-dependent checkpoint controls late-firing origins of DNA replication

Nature. 1998 Oct 8;395(6702):615-8. doi: 10.1038/27001.


DNA replication in eukaryotic cells initiates from many replication origins which fire throughout the S phase of the cell cycle in a predictable pattern: some origins fire early, others late. Little is known about how the initiation of DNA replication and the elongation of newly synthesized DNA strands are coordinated during S phase. Here we show that, in budding yeast, hydroxyurea, which blocks the progression of replication forks from early-firing origins, also inhibits the firing of late origins. These late origins are maintained in the initiation-competent prereplicative state for extended periods. The block to late origin firing is an active process and is defective in yeast with mutations in the rad53 and mec1 checkpoint genes, indicating that regulation of late origin firing may also be an important component of the 'intra-S-phase' checkpoint and may aid cell survival under adverse conditions.

MeSH terms

  • Cell Cycle
  • Cell Cycle Proteins / metabolism
  • Checkpoint Kinase 2
  • DNA Replication*
  • DNA, Fungal / biosynthesis*
  • Fungal Proteins / metabolism*
  • Hydroxyurea / pharmacology
  • Intracellular Signaling Peptides and Proteins
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases*
  • Replication Origin
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins*


  • CDC6 protein, S cerevisiae
  • Cell Cycle Proteins
  • DNA, Fungal
  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • Saccharomyces cerevisiae Proteins
  • Protein Kinases
  • Checkpoint Kinase 2
  • MEC1 protein, S cerevisiae
  • Protein-Serine-Threonine Kinases
  • RAD53 protein, S cerevisiae
  • Hydroxyurea