Abstract
Cdh1, a coactivator of the anaphase-promoting complex (APC), is a potential tumor suppressor. Cdh1 ablation promotes precocious S-phase entry, but it was unclear how this affects DNA replication dynamics while contributing to genomic instability and tumorigenesis. We find that Cdh1 depletion causes early S-phase onset in conjunction with increase in Rb/E2F1-mediated cyclin E1 expression, but reduced levels of cyclin E1 protein promote this transition. We hypothesize that this is due to a weakened cyclin-dependent kinase inhibitor (CKI)-cyclin-dependent kinase 2 positive-feedback loop, normally generated by APC-Cdh1-mediated proteolysis of Skp2. Indeed, Cdh1 depletion increases Skp2 abundance while diminishing levels of the CKI p27. This lowers the level of cyclin E1 needed for S-phase entry and delays cyclin E1 proteolysis during S-phase progression while corresponding to slowed replication fork movement and reduced frequency of termination events. In summary, using both experimental and computational approaches, we show that APC-Cdh1 establishes a stimulus-response relationship that promotes S phase by ensuring that proper levels of p27 accumulate during G1 phase, and defects in its activation accelerate the timing of S-phase onset while prolonging its progression.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Anaphase-Promoting Complex-Cyclosome / genetics*
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Anaphase-Promoting Complex-Cyclosome / metabolism
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Antigens, CD
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Cadherins / antagonists & inhibitors
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Cadherins / genetics*
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Cadherins / metabolism
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Cell Transformation, Neoplastic / genetics*
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Cell Transformation, Neoplastic / pathology
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Cyclin E / genetics
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Cyclin E / metabolism
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Cyclin-Dependent Kinase 2 / genetics
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Cyclin-Dependent Kinase 2 / metabolism
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Cyclin-Dependent Kinase Inhibitor p27 / genetics
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Cyclin-Dependent Kinase Inhibitor p27 / metabolism
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DNA Replication
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E2F1 Transcription Factor / genetics
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E2F1 Transcription Factor / metabolism
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Feedback, Physiological*
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G1 Phase
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Gene Expression Regulation
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HeLa Cells
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Humans
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Oncogene Proteins / genetics
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Oncogene Proteins / metabolism
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Proteolysis
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Retinoblastoma Protein / genetics
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Retinoblastoma Protein / metabolism
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S Phase*
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S-Phase Kinase-Associated Proteins / genetics
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S-Phase Kinase-Associated Proteins / metabolism
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Signal Transduction
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Time Factors
Substances
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Antigens, CD
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CCNE1 protein, human
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CDH1 protein, human
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Cadherins
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Cyclin E
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E2F1 Transcription Factor
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E2F1 protein, human
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Oncogene Proteins
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RNA, Small Interfering
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Retinoblastoma Protein
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S-Phase Kinase-Associated Proteins
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Cyclin-Dependent Kinase Inhibitor p27
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Anaphase-Promoting Complex-Cyclosome
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CDK2 protein, human
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Cyclin-Dependent Kinase 2