title: Origin association of Sld3, Sld7, and Cdc45 proteins is a key step for determination of origin-firing timing.
abstract: BACKGROUND
  Chromosomal DNA replication in eukaryotes initiates from multiple origins of replication, and because of this multiplicity, activation of replication origins is likely to be highly coordinated; origins fire at characteristic times, with some origins firing on average earlier (early-firing origins) and others later (late-firing origins) in the S phase of the budding yeast cell cycle. However, the molecular basis for such temporal regulation is poorly understood.
  
  
  RESULTS
  We show that origin association of the low-abundance replication proteins Sld3, Sld7, and Cdc45 is the key to determining the temporal order of origin firing. These proteins form a complex and associate with the early-firing origins in G1 phase in a manner that depends on Dbf4-dependent kinase (DDK), which is essential for the initiation of DNA replication. An increased dosage of Sld3, Sld7, and Cdc45 allows the late-firing origins to fire earlier in S phase. Additionally, an increased dosage of DDK also allows the late-firing origins to fire earlier.
  
  
  CONCLUSIONS
  The DDK-dependent limited association between origins and Sld3-Sld7-Cdc45 is a key step for determining the timing of origin firing.
authors.affiliation: Division of Microbial Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan. setanaka@lab.nig.ac.jp
authors.forename: Seiji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Nakato
authors.forename: Yuki
authors.initials: Y
authors.lastname: Katou
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Shirahige
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Araki
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D018741:Replication Origin; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C102209:CDC45 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C426020:Sld3 protein, S cerevisiae; C559742:Sld7 protein, S cerevisiae; C489404:CDC7 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases