Figure 4.

Gal4-PCAF-mediated stimulation of transcription is resistant to suppression by the adenoviral protein E1a. B78 cells were transfected with the reporter construct SP1-TATA-MG-Gal and expression vectors for Gal4-p300 and Gal4-PCAF. The transfection mixtures contained the CMV-promoter driven human growth hormone (hGH) gene as an internal control. The E1a gene was expressed from the Rous sarcoma virus (RSV) promoter in pRc/RSV (Invitrogen). (Upper) S1-nuclease assay using end-labeled probes homologous to the hGH gene and the MG reporter gene. (Lower) Quantitative PhosphorImager analyses of the S1-nuclease assay reveals a 4-fold decrease in Gal4-p300 mediated activation in the presence of E1a. In contrast, Gal4-PCAF stimulated transcription remains unaffected or increases slightly.