Modulation of pRb/E2F Functions in the Regulation of Cell Cycle and in Cancer
Lucy L. Seville, Nita Shah, Andrew D. Westwell and Weng C. Chan
Affiliation: School of Pharmacy, The Centre for Biomolecular Sciences, University of Nottingham, UniversityPark, Nottingham NG7 2RD, UK.
Cell proliferation is regulated by the cell cycle, and in order to divide the cell must enter a mitotic state. Prior to mitosis the cell is required to pass through a number of checkpoints, including the critical G1/S restriction point governed by the successive phosphorylation of the retinoblastoma protein, pRb. The various proteins and regulatory factors governing pRb phosphorylation have been a major focus of study in recent years, given the central importance of G1/S transition deregulation in cancer development. This review summarises the molecular biology around the G1/S transition, focussing on the critical roles of the transcription factor family E2F and the cyclin-dependent kinase (CDK) and cyclin families involved in E2F release from pRb. Interestingly, E2F release from pRb is associated with cell proliferation; however, above a certain threshold E2F has the potential to trigger apoptosis. The review focuses on the following topics: (i) how E2F and other substrates bind to pRb at the molecular level; (ii) mechanisms by which pRb function is modulated within the cell; (iii) mechanisms that inhibit or enhance cell proliferation via the pRb/E2F pathway; (iv) how E2F can potentiate apoptotic pathways; and (v) what controls whether E2F mediates cell proliferation or apoptosis. The case for the development of agents that perturb pRb:E2F interactions will be made, as a strategy to further inform the molecular biology around this important target and as a therapeutic strategy against cancer.
Keywords: cell proliferation, checkpoints, phosphorylation, apoptosis, cdks, ef family, transcription factor, transactivation domain, pocket-protein binding, rb gene
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