Transcription factor E4TF1 contains two subunits with different functions.

The transcription factor E4TF1 stimulates transcription from the adenovirus early region 4 promoter by binding to a specific promoter element. E4TF1 has been purified to homogeneity from HeLa cells by sequence-specific DNA affinity chromatography and characterized. E4TF1 is composed of at least two distinct subunits identified as 60 kd and 53 kd polypeptides. The 60 kd protein alone is able to bind to the specific DNA sequence but not to stimulate transcription in vitro. The 53 kd protein alone neither binds to DNA nor stimulates transcription in vitro. However, the 53 kd protein is able to interact with the 60 kd protein and the interaction confers the ability to stimulate transcription in vitro and to increase the DNA binding affinity of the 60 kd protein. This study provides evidence that the interaction between the two different subunits of E4TF1 is required for it to function as a transcription factor, and that one of the subunits binds to a specific DNA sequence and the other works as a modulator.