Feedback regulation between atypical E2Fs and APC/CCdh1 coordinates cell cycle progression

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• E2F transcription factors regulate cell cycle gene expression.
• Activator E2Fs (E2F1-3) promote G1-to-S transition, while atypical E2Fs (E2F7/8) downregulate targets in later phases.
• The inactivation mechanism of atypical E2Fs remained unclear.

Purpose of the Study:

• To investigate the inactivation mechanism of atypical E2Fs (E2F7 and E2F8).
• To elucidate the role of the anaphase-promoting complex/cyclosome (APC/C) in regulating E2F7/8 stability and function.

Main Methods:

• Ubiquitination assays to identify APC/C substrates.
• Mutagenesis of KEN boxes to assess E2F7/8 stability.
• Cell cycle analysis and cell viability assays.
• Co-immunoprecipitation to study protein interactions.

Main Results:

• E2F7 and E2F8 were identified as substrates of the APC/C complex.
• Mutations in CDH1-interacting KEN boxes stabilized E2F7/8, impairing G1-to-S transition and causing cell death.
• E2F8 interacts with APC/C(CDC20), while both E2F7/8 activate APC/C(CDH1) by repressing its inhibitors.

Conclusions:

• A novel feedback loop exists between atypical E2Fs and APC/C(CDH1).
• This loop is crucial for maintaining balanced cell cycle gene expression.
• The findings reveal a critical mechanism for normal cell cycle progression.