Activation of eukaryotic transcriptional promoters by the bovine papillomavirus E1-replication factor

It has been suggested that the bovine papillomavirus type 1 E1 replication factor may inhibit E2-conditional gene expression from viral promoter P89. To study the possible role of the E1 protein in gene expression, HeLa cells were transfected with E2-conditional or E2-independent reporter plasmids and with vectors expressing the E1 and E2 open reading frames. The data show that: (i) replication factor E1 stimulates gene expression from a variety of eucaryotic transcriptional promoters; (ii) activation of gene expression by E1 also occurs in the absence of viral activator E2-TA; (iii) expression of a recombinant plasmid containing the human papillomavirus type 18 origin of DNA replication is stimulated, but not repressed, by E1, and (iv) E1-dependent activation of gene expression does not reflect the amplification of transfected plasmids.