E2F transcription regulation: an orphan cyclin enters the stage.

Marked cyclin protein oscillations over the cell cycle ensure tight regulation of all cell cycle transitions. Despite expression patterns closely mirroring those of cyclin A, cyclin F has long been regarded as an odd outlier within the cyclin family. Constituting part of an E3 ubiquitin ligase, its main role was seen as highly restricted to timely degradation of very few key substrates to ensure termination of one error-free round of replication. Now, a recent series of studies suggests that cyclin F has very similar roles as its closest relatives, merely mediated through a very different mechanism.