A speculative model for E2F1 recruitment. (A) Classical E2F1 sites. At a subset of sites (mostly associated with cell cycle and DNA repair genes), E2F1 plays a major role in controlling transcriptional output by binding directly to a consensus site and helping to recruit the transcriptional machinery. (B) Cooperative E2F1 sites. At these sites, E2F1 binds cooperatively with other DNA-bound factors to sites that resemble the E2F consensus motif. (C) Inverted recruitment of E2F1. Here, E2F1 does not directly bind DNA, but perhaps is recruited to the promoter via interaction of the transactivation domain with general transcription factors such as TBP or TFIIH to play a role after pre-initiation complex formation. See Discussion for description.
