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Structural basis for the recognition of the E2F transactivation domain by the retinoblastoma tumor suppressor
Changwook Lee1, Jeong Ho Chang, Hyun Sook Lee
1National Creative Research Center for Structural Biology and Department of Life Science, Pohang University of Science and Technology, San 31, KyungBook, South Korea.
Abstract:
Repression of E2F transcription activity by the retinoblastoma (Rb) tumor suppressor through its interaction with the transactivation domain of the E2F transcription factor is one of the central features of G1/S arrest in the mammalian cell cycle. Deregulation of the Rb-E2F interaction results in hyperproliferation, lack of differentiation, and apoptosis, and can lead to cancer. The 2.2-A crystal structure of the Rb pocket complexed with an 18-residue transactivation-domain peptide of E2F-2 reveals that the boomerang-shaped peptide binds to the highly conserved interface between the A-box and the B-box of the Rb pocket in a bipartite manner. The N-terminal segment of the E2F-2 peptide in an extended beta-strand-like structure interacts with helices from the conserved groove at the A-B interface, whereas the C-terminal segment, which contains one 3(10) helix, binds to a groove mainly formed by A-box helices. The flexibility in the middle of the E2F-2 peptide is essential for the tight association of E2F to the Rb pocket. The binding of Rb to the E2F-2 peptide conceals several conserved residues that are crucial for transcription activation of E2F. We provide the structural basis for the Rb-mediated repression of E2F transcription activity without the requirement of histone-modifying enzymes.
Insights
The retinoblastoma (Rb) tumor suppressor represses E2F transcription activity, crucial for cell cycle arrest. This study reveals the structural basis of Rb-E2F interaction, essential for understanding cancer development.
Area of Science:
- Molecular Biology
- Structural Biology
- Cancer Research
Background:
- The retinoblastoma (Rb) protein is a key tumor suppressor regulating the cell cycle.
- Rb represses E2F transcription factor activity, a critical step in G1/S phase arrest.
- Dysregulation of the Rb-E2F interaction is linked to cancer development.
Purpose of the Study:
- To elucidate the structural mechanism of Rb-E2F interaction.
- To understand how Rb binding represses E2F transcription activity.
Main Methods:
- X-ray crystallography (2.2-Å resolution) of the Rb pocket complexed with an E2F-2 peptide.
- Structural analysis of the peptide-protein interface.
Main Results:
- The E2F-2 peptide adopts a boomerang shape and binds Rb in a bipartite manner at the A-B box interface.
- Specific interactions involve N-terminal beta-strand-like and C-terminal helical segments of E2F-2.
- Rb binding masks critical E2F residues essential for transcription activation.
Conclusions:
- The study provides the structural basis for Rb-mediated repression of E2F transcription.
- This repression occurs independently of histone-modifying enzymes.
- Understanding this interaction is vital for cancer research and therapeutic strategies.