Regulation of DNA-replication origins during cell-cycle progression.
We have shown previously that chromosome VI of Saccharomyces cerevisiae contains nine origins of DNA replication that differ in initiation frequency and replicate sequentially during the S phase of the cell cycle. Here we show that there are links between activation of these multiple origins and regulation of S-phase progression. We study the effects of a DNA-damaging agent, methyl methane sulphonate (MMS), and of mutations in checkpoint genes such as rad53 on the activity of origins, measured by two-dimensional gel analysis, and on cell-cycle progression, measured by fluorescence-activated cell sorting. We find that when MMS slows down S-phase progression it also selectively blocks initiation from late origins. A rad53 mutation enhances late and/or inefficient origins and releases the initiation block by MMS. Mutation of rad53 also results in a late origin becoming early replicating. We conclude that rad53 regulates the timing of initiation of replication from late origins during normal cell growth and blocks initiation from late origins in MMS-treated cells. rad53 is, therefore, involved in the cell's surveillance of S-phase progression. We also find that orc2, which encodes subunit 2 of the origin-recognition complex, is involved in suppression of late origins.
Nara Institute of Science and Technology, Ikoma, Japan.
K
K
Shirahige
Y
Y
Hori
K
K
Shiraishi
M
M
Yamashita
K
K
Takahashi
C
C
Obuse
T
T
Tsurimoto
H
H
Yoshikawa
D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D004261:DNA Replication / Q000502:physiology*; D004271:DNA, Fungal / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D051738:Origin Recognition Complex; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D018741:Replication Origin; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins
D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D009153:Mutagens; C497215:ORC2 protein, S cerevisiae; D051738:Origin Recognition Complex; D029701:Saccharomyces cerevisiae Proteins; D008741:Methyl Methanesulfonate; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae