Int J Biol Sci 2010; 6(2):116-128. doi:10.7150/ijbs.6.116 This issue

Research Paper

E2F-1 has dual roles depending on the cell cycle

Fikret Sahin1, 2, , Todd L. Sladek1, 3

1. Department of Microbiology and Immunology, Finch University of Health Sciences/Chicago Medical School (now Rosalind Franklin University), 3333 Green Bay Road, North Chicago, Illinois 60064-3095, USA
2. Current address: Microbiology Department, School of Medicine, Ankara University, Sihhiye-Ankara, Turkey
3. Current address: 3802 Sagamore Drive, Greensboro, NC 27410, USA

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Sahin F, Sladek TL. E2F-1 has dual roles depending on the cell cycle. Int J Biol Sci 2010; 6(2):116-128. doi:10.7150/ijbs.6.116. Available from

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The E2F family of transcription factors play a critical role in the control of cell proliferation. E2F-1 is the major cellular target of pRB and is regulated by pRB during cell proliferation. E2F-1-mediated activation and repression of target genes occurs in different settings. The role of E2F-1 and E2F-1/pRB complexes in regulation of different target genes, and in cycling versus quiescent cells, is unclear. In this study, effects of free E2F-1 (doesn't complex with pRb) and E2F-1/pRb complex, on E2F-1 target gene expression were compared in different cell growth conditions. Findings suggest that E2F-1 acts in different ways, not only depending on the target gene but also depending on different stages of the cell cycle. For example, E2F-1 acts as part of the repression complex with pRB in the expression of DHFR, b-myb, TK and cdc2 in asynchronously growing cells; on the other hand, E2F-1 acts as an activator in the expression of the same genes in cells that are re-entering the cycle.

Keywords: E2F-1, Rb, Cell cycle, cmyc, dhfr, TK, cdc2