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Published on: June 6, 2017
Cell cycle oscillators underlying orderly proteolysis of E2F8
Danit Wasserman1, Sapir Nachum1, Meital Cohen1
1Faculty of Life Sciences and Institute of Nanotechnology and Advanced Materials, Bar-llan University, Ramat-Gan 5290002, Israel.
Abstract:
E2F8 is a transcriptional repressor that antagonizes E2F1 at the crossroads of the cell cycle, apoptosis, and cancer. Previously, we discovered that E2F8 is a direct target of the APC/C ubiquitin ligase. Nevertheless, it remains unknown how E2F8 is dynamically controlled throughout the entirety of the cell cycle. Here, using newly developed human cell-free systems that recapitulate distinct inter-mitotic and G1 phases and a continuous transition from prometaphase to G1, we reveal an interlocking dephosphorylation switch coordinating E2F8 degradation with mitotic exit and the activation of APC/CCdh1. Further, we uncover differential proteolysis rates for E2F8 at different points within G1 phase, accounting for its accumulation in late G1 while APC/CCdh1 is still active. Finally, we demonstrate that the F-box protein Cyclin F regulates E2F8 in G2-phase. Altogether, our data define E2F8 regulation throughout the cell cycle, illuminating an extensive coordination between phosphorylation, ubiquitination and transcription in mammalian cell cycle.
Insights
Researchers uncovered how the E2F8 protein
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Ubiquitination and Proteolysis
Background:
- E2F8 acts as a transcriptional repressor, influencing cell cycle, apoptosis, and cancer.
- E2F8 is a known target of the APC/C ubiquitin ligase, but its cell cycle-specific regulation is unclear.
Purpose of the Study:
- To elucidate the dynamic control mechanisms of E2F8 throughout the entire cell cycle.
- To understand the interplay between E2F8 phosphorylation, ubiquitination, and transcriptional activity.
Main Methods:
- Utilized novel human cell-free systems to model inter-mitotic, G1, and prometaphase-to-G1 transitions.
- Investigated E2F8 degradation kinetics and regulation by APC/CCdh1 and Cyclin F.
Main Results:
- Identified a dephosphorylation switch that coordinates E2F8 degradation with mitotic exit and APC/CCdh1 activation.
- Revealed differential E2F8 proteolysis rates in G1, explaining its late G1 accumulation.
- Demonstrated Cyclin F's role in regulating E2F8 during the G2 phase.
Conclusions:
- Established a comprehensive model for E2F8 regulation across the cell cycle.
- Highlighted extensive coordination between phosphorylation, ubiquitination, and transcription in mammalian cell cycle control.
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