Polo-like Kinase-1 Controls Proteasome-Dependent Degradation of Claspin during Checkpoint Recovery

Mamely, Ivan; Vugt, Marcel A.T.M. van; Smits, Veronique A. J.; Semple, Jennifer I.; Lemmens, Bennie B. L. G.; Perrakis, Anastassis; Medema, René H.; Freire, Raimundo

doi:10.1016/j.cub.2006.08.026

Cited by 206 publications

(237 citation statements)

References 13 publications

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“…Three papers published during the review of this manuscript have identified amino acids 29-34 of Claspin as a phosphorylation-dependent proteasomal degradation motif required for binding of the ubiquitin ligase SCF b-TrCP to Claspin. [22][23][24] However, mutation of Ser30 and Ser34, which has been shown to abolish SCF b-TrCP -mediated degradation of Claspin [22][23][24] did not increase the stability of a caspaseresistant Claspin construct in apoptotic cells. These data indicate that the stability of Claspin during apoptosis is regulated by a ubiquitin ligase and/or a degradation signal different from that responsible for its degradation during normal cell cycle progression and recovery from checkpoint arrest.…”

Section: Discussionmentioning

confidence: 94%

Cleavage and degradation of Claspin during apoptosis by caspases and the proteasome

et al. 2007

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Apoptosis plays a crucial role in development and tissue homeostasis. Some key survival pathways, such as DNA damage checkpoints and DNA repair, have been described to be inactivated during apoptosis. Here, we describe the processing of the human checkpoint protein Claspin during apoptosis. We observed cleavage of Claspin into multiple fragments in vivo. In vitro cleavage with caspases 3 and 7 of various fragments of the protein, revealed cut sites near the N-and C-termini of the protein.Using mass spectrometry, we identified a novel caspase cleavage site in Claspin at Asp25. Importantly, in addition to cleavage by caspases, we observed a proteasome-dependent degradation of Claspin under apoptotic conditions, resulting in a reduction of the levels of both full-length Claspin and its cleavage products. This degradation was not dependent upon the DSGxxS phosphodegron motif required for SCF b-TrCP -mediated ubiquitination of Claspin. Finally, downregulation of Claspin protein levels by short interfering RNA resulted in an increase in apoptotic induction both in the presence and absence of DNA damage. We conclude that Claspin has antiapoptotic activity and is degraded by two different pathways during apoptosis. The resulting disappearance of Claspin from the cells further promotes apoptosis.

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Section: Discussionmentioning

confidence: 94%

Cleavage and degradation of Claspin during apoptosis by caspases and the proteasome

et al. 2007

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“…Under these conditions, Chk1 activity also remains high and hence the checkpoint remains engaged [34]. Several independent studies identified that this accumulation of Claspin is due to a defect in its' ubiquitin-dependent proteolysis by SCF complexes containing the β-TrCP F-box protein [35][36][37].…”

Section: Ubiquitin-dependent Proteolysis Of Activated Checkpoint Protmentioning

confidence: 99%

Turning off the G2 DNA damage checkpoint

Calonge

O’Connell

2008

DNA Repair

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In response to DNA damage, cells activate checkpoints to delay cell cycle progression and allow time for completion of DNA repair before commitment to S-phase or mitosis. During G2, many proteins collaborate to activate Chk1, an effector protein kinase that ensures the mitotic cyclindependent kinase remains in an inactive state. This checkpoint is ancient in origin and highly conserved from fission yeast to humans. Work from many groups has led to a detailed description of the spatiotemporal control of signaling events leading to Chk1 activation. However, to survive DNA damage in G2, the checkpoint must be inactivated to allow resumption of cell cycling and entry into mitosis. Though only beginning to be understood, here we review current data regarding checkpoint termination signals acting on Chk1 and its' upstream regulators.

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“…Dysfunction of topoIIa might generate DNA strand breaks and activate the DNA-damage checkpoint. In contrast, Plk1 is a target of the DNA-damage checkpoint and is required for checkpoint recovery after the damage has been completely repaired (Smits et al, 2000;Mamely et al, 2006). Plk1 interacts with several checkpoint components, such as p53 and Chk2 (Tsvetkov et al, 2003;Ando et al, 2004).…”

Section: Plk1 Depletion Activates Checkpointmentioning

confidence: 99%

Plk1 depletion in nontransformed diploid cells activates the DNA-damage checkpoint

Lei

Erikson

2008

Oncogene

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We previously reported that polo-like kinase 1 (Plk1) depletion by lentivirus-based RNA interference led to mitotic arrest and apoptosis in cancer cells, whereas normal diploid cell lines, hTERT-RPE1 and MCF10A, survived a similar level of depletion. To study homogeneous cell lines, we generated several Plk1-depleted hTERT-RPE1 and MCF10A clones that were derived from single cells depleted of Plk1. We found that in the long term, Plk1 depletion slowed proliferation of hTERT-RPE1 cells, apparently due to attenuated progression through S phase. These cells had altered morphology and were elongated compared with control. In contrast, MCF10A clones with mild levels of depletion showed no obvious phenotype. They appeared to have normal proliferation rates with no cell-cycle arrest. However, one MCF10A clone, which was severely depleted of Plk1, although viable, showed sporadic G2/M arrest and apoptosis. This MCF10A clone and all the hTERT-RPE1 clones displayed evidence of DNA-damage checkpoint activation. These data further support the interpretation that cancer cell lines have a much greater requirement for Plk1 than normal nontransformed diploid cells.

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Polo-like Kinase-1 Controls Proteasome-Dependent Degradation of Claspin during Checkpoint Recovery

Cited by 206 publications

References 13 publications

Cleavage and degradation of Claspin during apoptosis by caspases and the proteasome

Cleavage and degradation of Claspin during apoptosis by caspases and the proteasome

Turning off the G2 DNA damage checkpoint

Plk1 depletion in nontransformed diploid cells activates the DNA-damage checkpoint

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