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Caf1 regulates translocation of ribonucleotide reductase by releasing nucleoplasmic Spd1-Suc22 assembly.

Takahashi S, Kontani K, Araki Y, Katada T - Nucleic Acids Res. (2007)

Bottom Line: Here, we show that Caf1, a component of the Ccr4-Not complex, is responsible for resistance of the replication stress and control of the Suc22 translocation.DNA-replication stress appears to allow Caf1 to interact with Suc22, resulting in release of the nucleoplasmic Spd1-Suc22 assembly.Taken together, these results suggest a novel function of Caf1 as a key regulator in the stress-induced RNR activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.

ABSTRACT
Appropriate supply of deoxyribonucleotides by the ribonucleotide reductase (RNR) complex is essential for DNA replication and repair. One recent model for the RNR activation in Schizosaccharomyces pombe is translocation of the regulatory subunit Suc22 from the nucleoplasm to the cytoplasm. The RNR inhibitory protein Spd1, which retains Suc22 in the nucleoplasm, is rapidly degraded upon DNA-replication stress, resulting in release of Suc22 to form the active RNR complex in the cytoplasm. Here, we show that Caf1, a component of the Ccr4-Not complex, is responsible for resistance of the replication stress and control of the Suc22 translocation. Caf1 is required not only for the stress-induced translocation of Suc22 from nucleoplasm to cytoplasm but also for the degradation of nucleoplasmic Spd1. DNA-replication stress appears to allow Caf1 to interact with Suc22, resulting in release of the nucleoplasmic Spd1-Suc22 assembly. Taken together, these results suggest a novel function of Caf1 as a key regulator in the stress-induced RNR activation.

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Caf1 is required for the cytoplasmic translocation of Suc22 in response to DNA-replication stress. Logarithmically growing cells, wild type (A, YSP001), spd1Δ (B, YSP112) and caf1Δ (C, YSP066), were incubated in the presence and absence of 10 mM HU for 2 h at 30°C. Immunofluorescence-staining images of Suc22 were obtained with an anti-Suc22 antibody.
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Figure 4: Caf1 is required for the cytoplasmic translocation of Suc22 in response to DNA-replication stress. Logarithmically growing cells, wild type (A, YSP001), spd1Δ (B, YSP112) and caf1Δ (C, YSP066), were incubated in the presence and absence of 10 mM HU for 2 h at 30°C. Immunofluorescence-staining images of Suc22 were obtained with an anti-Suc22 antibody.

Mentions: The RNR activity is stimulated through the interaction of Suc22 with Cdc22 in the cytoplasm. However, translocation of Suc22 into cytoplasm is inhibited by nuclear Spd1 through the formation of a nucleoplasmic Spd1–Suc22 assembly. In S phase, degradation of Spd1 via the Pcu4–Ddb1–CSN complex leads Suc22 to be exported to cytoplasm (27). To explore the undescribed function of Caf1 in HU-induced stress response, we next investigated subcellular localization of the components of RNR pathway (Figure 4). In the absence of the replication stress, Suc22 was localized in the nucleoplasm of both wild-type and caf1Δ cells. In contrast, Suc22 dispersed into the cytoplasm in spd1Δ cells is probably due to the loss of the ability to retain the nucleoplasmic Suc22. After HU treatment, the cytoplasmic signal of Suc22 was detected in wild type cells. However, the localization of Suc22 was not altered in caf1Δ cells even after the HU treatment. These results indicate that Caf1 is required for HU-induced cytoplasmic translocation of Suc22.Figure 4.


Caf1 regulates translocation of ribonucleotide reductase by releasing nucleoplasmic Spd1-Suc22 assembly.

Takahashi S, Kontani K, Araki Y, Katada T - Nucleic Acids Res. (2007)

Caf1 is required for the cytoplasmic translocation of Suc22 in response to DNA-replication stress. Logarithmically growing cells, wild type (A, YSP001), spd1Δ (B, YSP112) and caf1Δ (C, YSP066), were incubated in the presence and absence of 10 mM HU for 2 h at 30°C. Immunofluorescence-staining images of Suc22 were obtained with an anti-Suc22 antibody.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1851654&req=5

Figure 4: Caf1 is required for the cytoplasmic translocation of Suc22 in response to DNA-replication stress. Logarithmically growing cells, wild type (A, YSP001), spd1Δ (B, YSP112) and caf1Δ (C, YSP066), were incubated in the presence and absence of 10 mM HU for 2 h at 30°C. Immunofluorescence-staining images of Suc22 were obtained with an anti-Suc22 antibody.
Mentions: The RNR activity is stimulated through the interaction of Suc22 with Cdc22 in the cytoplasm. However, translocation of Suc22 into cytoplasm is inhibited by nuclear Spd1 through the formation of a nucleoplasmic Spd1–Suc22 assembly. In S phase, degradation of Spd1 via the Pcu4–Ddb1–CSN complex leads Suc22 to be exported to cytoplasm (27). To explore the undescribed function of Caf1 in HU-induced stress response, we next investigated subcellular localization of the components of RNR pathway (Figure 4). In the absence of the replication stress, Suc22 was localized in the nucleoplasm of both wild-type and caf1Δ cells. In contrast, Suc22 dispersed into the cytoplasm in spd1Δ cells is probably due to the loss of the ability to retain the nucleoplasmic Suc22. After HU treatment, the cytoplasmic signal of Suc22 was detected in wild type cells. However, the localization of Suc22 was not altered in caf1Δ cells even after the HU treatment. These results indicate that Caf1 is required for HU-induced cytoplasmic translocation of Suc22.Figure 4.

Bottom Line: Here, we show that Caf1, a component of the Ccr4-Not complex, is responsible for resistance of the replication stress and control of the Suc22 translocation.DNA-replication stress appears to allow Caf1 to interact with Suc22, resulting in release of the nucleoplasmic Spd1-Suc22 assembly.Taken together, these results suggest a novel function of Caf1 as a key regulator in the stress-induced RNR activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.

ABSTRACT
Appropriate supply of deoxyribonucleotides by the ribonucleotide reductase (RNR) complex is essential for DNA replication and repair. One recent model for the RNR activation in Schizosaccharomyces pombe is translocation of the regulatory subunit Suc22 from the nucleoplasm to the cytoplasm. The RNR inhibitory protein Spd1, which retains Suc22 in the nucleoplasm, is rapidly degraded upon DNA-replication stress, resulting in release of Suc22 to form the active RNR complex in the cytoplasm. Here, we show that Caf1, a component of the Ccr4-Not complex, is responsible for resistance of the replication stress and control of the Suc22 translocation. Caf1 is required not only for the stress-induced translocation of Suc22 from nucleoplasm to cytoplasm but also for the degradation of nucleoplasmic Spd1. DNA-replication stress appears to allow Caf1 to interact with Suc22, resulting in release of the nucleoplasmic Spd1-Suc22 assembly. Taken together, these results suggest a novel function of Caf1 as a key regulator in the stress-induced RNR activation.

Show MeSH
Related in: MedlinePlus