FIG. 7.

Model for activation of the human PCNA promoter by E1A 243R. Schematic diagram of the minimal PCNA-E1A-responsive promoter is illustrated with the cis-acting PERE boxed in gray, the RFX1-binding site, and the cellular factors indicated. A possible mechanism by which E1A 243R might transactivate the PCNA promoter is depicted sequentially. (A) E1A 243R first targets the PCNA promoter at the PERE site via a CBP-CREB-PERE pathway (37). (B) The binding between E1A and CBP activates the promoter by itself through an interaction between CBP and components of the general transcription machinery (general transcription factors [GTFs]). (C) E1A 243R increases PCNA promoter expression by mediating the relief of a transcriptional repression exerted on the promoter by p107. Note that the events depicted in panels B and C might take place simultaneously.