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Updated: May 13, 2026

Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Cell cycle regulation of the E2F transcription factor involves an interaction with cyclin A
M Mudryj1, S H Devoto, S W Hiebert
1Howard Hughes Medical Institute, Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710.
Abstract:
We have examined E2F binding activity in extracts of synchronized NIH 3T3 cells. During the G0 to G1 transition, there is a marked increase in the level of active E2F. Subsequently, there are changes in the nature of E2F-containing complexes. A G1-specific complex increases in abundance, disappears, and is then replaced by another complex as S phase begins. Analysis of extracts of thymidine-blocked cells confirms that the complexes are cell cycle regulated. We also show that the cyclin A protein is a component of the S phase complex. Each complex can be dissociated by the adenovirus E1A 12S product, releasing free E2F. The release of E2F from the cyclin A complex coincides with the stimulation of an E2F-dependent promoter. We suggest that these interactions control the activity of E2F and that disruption of the complexes by E1A contributes to a loss of cellular proliferation control.
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