Structural mechanism for the recognition of E2F1 by the ubiquitin ligase adaptor Cyclin F

• 成果类型: Article
• 署名作者: Ngoi, Peter; Wang, Xianxi; Putta, Sivasankar; Da Luz, Ricardo F.; Serrao, Vitor Hugo B.; Emanuele, Michael J.; Rubin, Seth M.
• 署名单位: University of California System; University of California Santa Cruz; University of North Carolina; University of North Carolina Chapel Hill; University of North Carolina; University of North Carolina Chapel Hill; University of California System; University of California Santa Cruz
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14761
• DOI: 10.1073/pnas.2501057122
• 发表日期: 2025-07-01
• 关键词: dependent kinase 2; RECRUITMENT; complex; protein; refinement; binding; roles; motif; site

摘要

Cyclin F, a noncanonical member of the cyclin protein family, plays a critical role in regulating transitions in the cell division cycle. Unlike canonical cyclins, which bind and activate cyclin-dependent kinases (CDKs), Cyclin F functions as a substrate receptor protein within the Skp1-Cullin-F-box E3 ubiquitin ligase complex, enabling the ubiquitylation of target proteins. The structural features that distinguish Cyclin F as a ligase adaptor and the mechanisms underlying its selective substrate recruitment over Cyclin A, which functions in complex with CDK2 at a similar time in the cell cycle, remain largely unexplored. We utilized single-particle cryoelectron microscopy to elucidate the structure of a Cyclin F-Skp1 complex bound to an E2F1 peptide. The structure and biochemical analysis reveal important differences in the substrate-binding site of Cyclin F compared to Cyclin A. Our findings expand on the canonical cyclin-binding motif (Cy or RxL) and highlight the importance of electrostatics at the E2F1 binding interface, which varies between Cyclin F and Cyclin A. These results advance our understanding of E2F1 regulation and may inform strategies for selectively targeting Cyclin F in cancer or neurodegeneration. Significance Cyclin F is an essential enzyme that mediates cell division by downregulating activity of the E2F transcription factor. Unlike other members of the cyclin family, Cyclin F does not activate cyclin-dependent kinases, but rather it mediates degradation of substrates, including E2F. We determined the structure of an E2F1-Cyclin F complex to address two important questions: What are the structural properties of Cyclin F that confer its unique ligase adaptor function, and how does Cyclin F recognize its substrates with the right specificity? The data reveal a Cyclin F structural domain that prevents kinase association and active site features that mediate substrate binding. These data will help us understand Cyclin Ffunction and realize its potential as a therapeutic target.