The fission yeast cdc18+ gene product couples S phase to START and mitosis

Kelly, Thomas J.; Martin, G S; Forsburg, Susan L.; Stephen, Robert J.; Russo, Alicia A.; Nurse, Paul

doi:10.1016/0092-8674(93)90427-r

Cited by 447 publications

(428 citation statements)

References 53 publications

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“…Overexpression of either Cdc18 (the homolog of Cdc6) or of the CDK inhibitor Rum1 (the homolog/analog of Sic1) is sufficient for rereplication in S. pombe (Kelly et al, 1993;Moreno and Nurse, 1994;Nishitani and Nurse, 1995;Lopez-Girona et al, 1998), whereas the equivalent manipulations do not cause rereplication in S. cerevisiae. It is still somewhat unclear to what extent the rereplication caused by overexpression of Cdc18 is due to its activity as a CDK inhibitor, versus its activity as a replication inititator.…”

Section: Discussionmentioning

confidence: 99%

Roles of the CDK Phosphorylation Sites of Yeast Cdc6 in Chromatin Binding and Rereplication

Honey

Futcher

2007

MBoC

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The Saccharomyces cerevisiae Cdc6 protein is crucial for DNA replication. In the absence of cyclin-dependent kinase (CDK) activity, Cdc6 binds to replication origins, and loads Mcm proteins. In the presence of CDK activity, Cdc6 does not bind to origins, and this helps prevent rereplication. CDK activity affects Cdc6 function by multiple mechanisms: CDK activity affects transcription of CDC6, degradation of Cdc6, nuclear import of Cdc6, and binding of Cdc6 to Clb2. Here we examine some of these mechanisms individually. We find that when Cdc6 is forced into the nucleus during late G1 or S, it will not substantially reload onto chromatin no matter whether its CDK sites are present or not. In contrast, at a G2/M nocodazole arrest, Cdc6 will reload onto chromatin if and only if its CDK sites have been removed. Trace amounts of nonphosphorylatable Cdc6 are dominant lethal in strains bearing nonphosphorylatable Orc2 and Orc6, apparently because of rereplication. This synthetic dominant lethality occurs even in strains with wild-type MCM genes. Nonphosphorylatable Cdc6, or Orc2 and Orc6, sensitize cells to rereplication caused by overexpression of various replication initiation proteins such as Dpb11 and Sld2.

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Section: Discussionmentioning

confidence: 99%

Roles of the CDK Phosphorylation Sites of Yeast Cdc6 in Chromatin Binding and Rereplication

Honey

Futcher

2007

MBoC

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“…It is reasonable to propose that the negative regulation of Cdc18 that is catalyzed by Cdc2 kinase may be only one part of the mechanism by which Cdc2 kinase prevents reactivation of replication origins following the onset of S phase. In the normal cell cycle, cdc18 ϩ mRNA expression is limited to S phase by a process that may also be controlled by Cdc2 (Kelly et al, 1993;Nishitani and Nurse, 1995;Muzi-Falconi et al, 1996b). This transcriptional regulation of cdc18 ϩ , coupled with the short half-life of Cdc18 protein that may also be regulated by Cdc2, may collaborate to provide a fail-safe mechanism that prevents inappropriate activation of replication origins following the onset of S phase.…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies of fission yeast have suggested that the Cdc18 protein plays an important role in regulating chromosomal DNA replication. The cdc18 ϩ gene is essential for initiation of DNA replication (Nasmyth and Nurse, 1981;Kelly et al, 1993). High constitutive expression of Cdc18 protein causes cells to undergo continuous DNA replication without intervening mitosis, whereas cells deleted for the cdc18 ϩ gene bypass S phase and enter mitosis directly from G 1 (Kelly et al, 1993;Nishitani and Nurse, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…The cdc18 ϩ gene is essential for initiation of DNA replication (Nasmyth and Nurse, 1981;Kelly et al, 1993). High constitutive expression of Cdc18 protein causes cells to undergo continuous DNA replication without intervening mitosis, whereas cells deleted for the cdc18 ϩ gene bypass S phase and enter mitosis directly from G 1 (Kelly et al, 1993;Nishitani and Nurse, 1995). The levels of cdc18 ϩ mRNA and protein are highly periodic during the cell cycle, being absent in G 1 , peaking during S phase and returning to a very low level during G 2 and M (Nishitani and Nurse, 1995;Muzi-Falconi et al, 1996b).…”

Section: Introductionmentioning

confidence: 99%

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Negative Regulation of Cdc18 DNA Replication Protein by Cdc2

López-Girona

Mondésert

Leatherwood

et al. 1998

MBoC

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Fission yeast Cdc18, a homologue of Cdc6 in budding yeast and metazoans, is periodically expressed during the S phase and required for activation of replication origins. Cdc18 overexpression induces DNA rereplication without mitosis, as does elimination of Cdc2-Cdc13 kinase during G2 phase. These findings suggest that illegitimate activation of origins may be prevented through inhibition of Cdc18 by Cdc2. Consistent with this hypothesis, we report that Cdc18 interacts with Cdc2 in association with Cdc13 and Cig2 B-type cyclins in vivo. Cdc18 is phosphorylated by the associated Cdc2 in vitro. Mutation of a single phosphorylation site, T104A, activates Cdc18 in the rereplication assay. The cdc18-K9 mutation is suppressed by a cig2 mutation, providing genetic evidence that Cdc2-Cig2 kinase inhibits Cdc18. Moreover, constitutive expression of Cig2 prevents rereplication in cells lacking Cdc13. These findings identify Cdc18 as a key target of Cdc2-Cdc13 and Cdc2-Cig2 kinases in the mechanism that limits chromosomal DNA replication to once per cell cycle.

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“…(27) Later, it was identified in Schizosaccharomyces pombe as a key regulator of chromosome ploidy (28) and again in S. cerevisiae as a suppressor of ORC mutations. (29) CDC6 is conserved in all eukarya and it encodes an AAA þ protein with significant sequence similarity to Orc1.…”

Section: Introductionmentioning

confidence: 99%

Perpetuating the double helix: molecular machines at eukaryotic DNA replication origins

2003

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SummaryThe hardest part of replicating a genome is the beginning. The first step of DNA replication (called ''initiation'') mobilizes a large number of specialized proteins (''initiators'') that recognize specific sequences or structural motifs in the DNA, unwind the double helix, protect the exposed ssDNA, and recruit the enzymatic activities required for DNA synthesis, such as helicases, primases and polymerases. All of these components are orderly assembled before the first nucleotide can be incorporated. On the occasion of the 50th anniversary of the discovery of the DNA structure, we review our current knowledge of the molecular mechanisms that control initiation of DNA replication in eukaryotic cells, with particular emphasis on the recent identification of novel initiator proteins. We speculate how these initiators assemble molecular machines capable of performing specific biochemical tasks, such as loading a ringshaped helicase onto the DNA double helix.

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The fission yeast cdc18+ gene product couples S phase to START and mitosis

Cited by 447 publications

References 53 publications

Roles of the CDK Phosphorylation Sites of Yeast Cdc6 in Chromatin Binding and Rereplication

Roles of the CDK Phosphorylation Sites of Yeast Cdc6 in Chromatin Binding and Rereplication

Negative Regulation of Cdc18 DNA Replication Protein by Cdc2

Perpetuating the double helix: molecular machines at eukaryotic DNA replication origins

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