CBF mediates adenovirus Ela trans-activation by interaction at the C-terminal promoter targeting domain of conserved region 3.

Genetic and biochemical evidence suggest that conserved region 3 (CR3) of the adenovirus Ela polypeptide can provide two distinct and separable functions: an N-terminal transcriptional activation region and a C-terminal promoter targeting region. It is thought that the promoter targeting region of Ela CR3 interacts with promoter-specific transcription factors, thereby bringing the activation region of Ela CR3 in proximity of the promoter. Here we report that CBF, a CCAAT-box-binding factor that regulates hsp70 gene expression and mediates Ela trans-activation in vivo, interacts with the promoter targeting region of Ela CR3 in vitro. Point mutations in Ela CR3 that are defective in stimulating transcription from the hsp70 promoter are also defective in stimulating transcription directed by a synthetic activator, GAL-CBF, composed of the DNA-binding domain of yeast GAL4 fused to CBF. These mutations fall into two classes with respect to their abilities to interact with CBF in vitro. Mutations in the transcriptional activation region of Ela CR3 do not affect binding to CBF, but mutation of the promoter targeting region of Ela CR3 prevents association with CBF in vitro.