The adenovirus E1A transforming protein activates the proliferating cell nuclear antigen promoter via an activating transcription factor site.

The transforming region of adenovirus (E1) stimulates expression of a reporter construct linked to the promoter for the human proliferating cell nuclear antigen (PCNA) gene in a cotransfection assay (G. F. Morris and M. B. Mathews, J. Biol. Chem. 264:13856-13864, 1989). The major products of the E1 region were assessed individually for their contribution to transactivation of the PCNA promoter. The E1A 13S and 12S products and the E1B 19-kDa product elevated expression from the PCNA promoter, whereas the E1B 55-kDa product did not. Induction of the PCNA promoter by E1A differed from transcriptional activation of the adenovirus E3 promoter in that the PCNA promoter is activated by the E1A 12S product whereas the E3 promoter is repressed; furthermore, the PCNA promoter is activated upon E1A overexpression, whereas the E3 promoter responds less well to high amounts of E1A. A site for the activating transcription factor ATF located approximately 50 nucleotides upstream from the transcription initiation site in the PCNA promoter mediates a positive response to the E1A 12S and 13S products.