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The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor.

Ivanova T, Alves-Rodrigues I, Gómez-Escoda B, Dutta C, DeCaprio JA, Rhind N, Hidalgo E, Ayté J - Mol. Biol. Cell (2013)

Bottom Line: We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription.This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin.This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, Barcelona 08003, Spain Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605 Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115.

ABSTRACT
In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex.

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A model for the integration of the DNA damage and the DNA replication checkpoints on the MBF complex. On replicative stress, fission yeast cells activate the effector kinase Cds1. Among its targets, the repressor Yox1 is phosphorylated and no longer can bind the MBF complex, alleviating the transcriptional repression of genes required for DNA synthesis. On DNA damage, the effector kinase Chk1 phosphorylates Cdc10, which is a core component of the MBF complex. The outcome of this phosphorylation is, contrary to what happens under replicative stress, release of Cdc10 from its target promoters and repression of MBF-dependent transcription.
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Figure 7: A model for the integration of the DNA damage and the DNA replication checkpoints on the MBF complex. On replicative stress, fission yeast cells activate the effector kinase Cds1. Among its targets, the repressor Yox1 is phosphorylated and no longer can bind the MBF complex, alleviating the transcriptional repression of genes required for DNA synthesis. On DNA damage, the effector kinase Chk1 phosphorylates Cdc10, which is a core component of the MBF complex. The outcome of this phosphorylation is, contrary to what happens under replicative stress, release of Cdc10 from its target promoters and repression of MBF-dependent transcription.

Mentions: The MBF complex is an essential transcription factor that fission yeast cells need for the normal and controlled expression of the S-phase transcription program. When DNA replication is challenged (e.g., after treatment of cells with HU), fission yeast cells activate their effector kinase (Cds1) and, among many other effects, are able to maintain a high level of MBF-dependent transcription (Gomez-Escoda et al., 2011). Because ribonucleotide reductase (Cdc22) is the target of HU and its expression is directly regulated by MBF (Lowndes et al., 1992), hyperactivation of the complex might help to overcome the block to DNA replication inflicted by the drug. Similar processes have been described in the distantly related budding yeast (de Bruin et al., 2008; Bastos de Oliveira et al., 2012; Travesa et al., 2012) and might be conserved to some extent in higher eukaryotes. Yox1, the repressor of the MBF complex, is the main MBF target of fission yeast Cds1 (Aligianni et al., 2009; Gomez-Escoda et al., 2011). Yox1 phosphorylation by Cds1 results in its inactivation (Caetano et al., 2011; Gomez-Escoda et al., 2011; Ivanova et al., 2011; Purtill et al., 2011). We now report here that the DNA damage checkpoint exerts a new layer of control on the MBF complex. However, instead of exerting a positive effect on MBF, Chk1, the effector kinase of the DNA damage checkpoint, is responsible for inactivating MBF-dependent transcription (Figure 7). This is achieved by direct phosphorylation of one of the core components of the MBF complex, Cdc10, at two different sites on its carboxy-terminal domain. This phosphorylation induces the exit of Cdc10 from the chromatin and thus the repression of the transcription of the MBF-dependent genes. Of interest, low doses of MMS are able to induce MBF-dependent transcription (probably through Cds1-dependent phosphorylation of Yox1), whereas high doses repress the same set of genes by directly phosphorylating Cdc10. In fact, under such severe damage there is no active MBF complex associated with the corresponding promoters, since Res1 and Res2 are also released from chromatin (Figure 2, B and C). Our hypothesis is that cells that have to cope with severe DNA damage must stop any attempt to initiate DNA synthesis, which will worsen its situation; this is achieved by switching off the S-phase transcriptional program. However, fission yeast cells sense discrete or minor DNA damage (low MMS concentration, HU) at least partly as a block to DNA synthesis, activating the DNA replication checkpoint. Consequently, these cells need to maintain activated the transcriptional S-phase program until they manage to fully complete the duplication of its genome. In conclusion, MBF would be doubly targeted by the DNA replication and the DNA damage checkpoints with outcomes that go in opposite directions: whereas the DNA damage checkpoint targets Cdc10 and causes repression, the DNA replication checkpoint phosphorylates Yox1 and induces activation of transcription. Of interest, whereas all of the MBF-dependent genes are induced upon a challenge to DNA replication (Dutta et al., 2008; Gomez-Escoda et al., 2011), only a subset seems to be under the control of the DNA damage checkpoint (Figure 6). We do not know how this is achieved, but it has long been known that not all MBF-dependent genes are regulated in the same manner; for example, in synchronized cultures, transcription of cdc18 is induced in anaphase, whereas induction of cig2 takes place later during the G1-to-S transition (Baum et al., 1997). Thus the differential regulation of the MBF-dependent genes by the DNA damage checkpoint may be due to intrinsically differences in the chromatin structure of the two groups of MBF dependent genes; alternatively, we have not excluded that other components or regulators of the MBF complex can be overlapping targets for Chk1 and play a role in only a subset of MBF-dependent genes. Further work is required to characterize this differential regulation.


The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor.

Ivanova T, Alves-Rodrigues I, Gómez-Escoda B, Dutta C, DeCaprio JA, Rhind N, Hidalgo E, Ayté J - Mol. Biol. Cell (2013)

A model for the integration of the DNA damage and the DNA replication checkpoints on the MBF complex. On replicative stress, fission yeast cells activate the effector kinase Cds1. Among its targets, the repressor Yox1 is phosphorylated and no longer can bind the MBF complex, alleviating the transcriptional repression of genes required for DNA synthesis. On DNA damage, the effector kinase Chk1 phosphorylates Cdc10, which is a core component of the MBF complex. The outcome of this phosphorylation is, contrary to what happens under replicative stress, release of Cdc10 from its target promoters and repression of MBF-dependent transcription.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 7: A model for the integration of the DNA damage and the DNA replication checkpoints on the MBF complex. On replicative stress, fission yeast cells activate the effector kinase Cds1. Among its targets, the repressor Yox1 is phosphorylated and no longer can bind the MBF complex, alleviating the transcriptional repression of genes required for DNA synthesis. On DNA damage, the effector kinase Chk1 phosphorylates Cdc10, which is a core component of the MBF complex. The outcome of this phosphorylation is, contrary to what happens under replicative stress, release of Cdc10 from its target promoters and repression of MBF-dependent transcription.
Mentions: The MBF complex is an essential transcription factor that fission yeast cells need for the normal and controlled expression of the S-phase transcription program. When DNA replication is challenged (e.g., after treatment of cells with HU), fission yeast cells activate their effector kinase (Cds1) and, among many other effects, are able to maintain a high level of MBF-dependent transcription (Gomez-Escoda et al., 2011). Because ribonucleotide reductase (Cdc22) is the target of HU and its expression is directly regulated by MBF (Lowndes et al., 1992), hyperactivation of the complex might help to overcome the block to DNA replication inflicted by the drug. Similar processes have been described in the distantly related budding yeast (de Bruin et al., 2008; Bastos de Oliveira et al., 2012; Travesa et al., 2012) and might be conserved to some extent in higher eukaryotes. Yox1, the repressor of the MBF complex, is the main MBF target of fission yeast Cds1 (Aligianni et al., 2009; Gomez-Escoda et al., 2011). Yox1 phosphorylation by Cds1 results in its inactivation (Caetano et al., 2011; Gomez-Escoda et al., 2011; Ivanova et al., 2011; Purtill et al., 2011). We now report here that the DNA damage checkpoint exerts a new layer of control on the MBF complex. However, instead of exerting a positive effect on MBF, Chk1, the effector kinase of the DNA damage checkpoint, is responsible for inactivating MBF-dependent transcription (Figure 7). This is achieved by direct phosphorylation of one of the core components of the MBF complex, Cdc10, at two different sites on its carboxy-terminal domain. This phosphorylation induces the exit of Cdc10 from the chromatin and thus the repression of the transcription of the MBF-dependent genes. Of interest, low doses of MMS are able to induce MBF-dependent transcription (probably through Cds1-dependent phosphorylation of Yox1), whereas high doses repress the same set of genes by directly phosphorylating Cdc10. In fact, under such severe damage there is no active MBF complex associated with the corresponding promoters, since Res1 and Res2 are also released from chromatin (Figure 2, B and C). Our hypothesis is that cells that have to cope with severe DNA damage must stop any attempt to initiate DNA synthesis, which will worsen its situation; this is achieved by switching off the S-phase transcriptional program. However, fission yeast cells sense discrete or minor DNA damage (low MMS concentration, HU) at least partly as a block to DNA synthesis, activating the DNA replication checkpoint. Consequently, these cells need to maintain activated the transcriptional S-phase program until they manage to fully complete the duplication of its genome. In conclusion, MBF would be doubly targeted by the DNA replication and the DNA damage checkpoints with outcomes that go in opposite directions: whereas the DNA damage checkpoint targets Cdc10 and causes repression, the DNA replication checkpoint phosphorylates Yox1 and induces activation of transcription. Of interest, whereas all of the MBF-dependent genes are induced upon a challenge to DNA replication (Dutta et al., 2008; Gomez-Escoda et al., 2011), only a subset seems to be under the control of the DNA damage checkpoint (Figure 6). We do not know how this is achieved, but it has long been known that not all MBF-dependent genes are regulated in the same manner; for example, in synchronized cultures, transcription of cdc18 is induced in anaphase, whereas induction of cig2 takes place later during the G1-to-S transition (Baum et al., 1997). Thus the differential regulation of the MBF-dependent genes by the DNA damage checkpoint may be due to intrinsically differences in the chromatin structure of the two groups of MBF dependent genes; alternatively, we have not excluded that other components or regulators of the MBF complex can be overlapping targets for Chk1 and play a role in only a subset of MBF-dependent genes. Further work is required to characterize this differential regulation.

Bottom Line: We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription.This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin.This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress and Cell Cycle Group, Universitat Pompeu Fabra, Barcelona 08003, Spain Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605 Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115.

ABSTRACT
In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex.

Show MeSH
Related in: MedlinePlus