title: Checkpoint-independent scaling of the Saccharomyces cerevisiae DNA replication program.
abstract: BACKGROUND
  In budding yeast, perturbations that prolong S phase lead to a proportionate delay in the activation times of most origins. The DNA replication checkpoint was implicated in this scaling phenotype, as an intact checkpoint was shown to be required for the delayed activation of late origins in response to hydroxyurea treatment. In support of that, scaling is lost in cells deleted of mrc1, a mediator of the replication checkpoint signal. Mrc1p, however, also plays a role in normal replication.
  
  
  RESULTS
  To examine whether the replication checkpoint is required for scaling the replication profile with S phase duration we measured the genome-wide replication profile of different MRC1 alleles that separate its checkpoint function from its role in normal replication, and further analyzed the replication profiles of S phase mutants that are checkpoint deficient. We found that the checkpoint is not required for scaling; rather the unique replication phenotype of mrc1 deleted cells is attributed to the role of Mrc1 in normal replication. This is further supported by the replication profiles of tof1Δ which functions together with Mrc1p in normal replication, and by the distinct replication profiles of specific POL2 alleles which differ in their interaction with Mrc1p.
  
  
  CONCLUSIONS
  We suggest that the slow fork progression in mrc1 deleted cells reduces the likelihood of passive replication leading to the activation of origins that remain mostly dormant in wild-type cells.
authors.forename: Ariel
authors.initials: A
authors.lastname: Gispan
authors.forename: Miri
authors.initials: M
authors.lastname: Carmi
authors.forename: Naama
authors.initials: N
authors.lastname: Barkai
mesh_terms: D000483:Alleles; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D004257:DNA Polymerase II / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D004271:DNA, Fungal / Q000096:biosynthesis* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C441579:MRC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C119636:TOF1 protein, S cerevisiae; D004257:DNA Polymerase II