TRANSCRIPTION STIMULATION OF THE ADENOVIRUS-TYPE-12 E1A GENE IN-VITROBY THE 266-AMINO-ACID E1A PROTEIN

We previously showed that the 13S but not the 12S mRNA product of the E1a gene of the highly oncogenic type 12 adenovirus (Ad12) stimulates the expression of its own gene. In this study, the mechanism for the a utoregulation of the Ad12 E1a gene was investigated in vitro. The 266- amino-acid E1A protein of Ad12 was synthesized in yeast cells and puri fied as a 57-kDa polypeptide. The purified Ad12 E1A protein stimulated transcription from the proximal promoter of its own gene but had almo st no effect on that from the distal promoter. A 35-bp upstream region including a TATA box for the proximal promoter seemed to be sufficien t for transcription stimulation by the E1A protein. The Ad12 E1A prote in formed a complex with a TATA box-binding protein (TBP), as does the E1A protein of nononcogenic Ad serotypes. Moreover, the E1A protein s ignificantly reduced the binding of TBP to a TATA sequence, while it d id not affect the DNA-binding activity of nuclear factor I, a stimulat ory protein of the distal transcription of the Ad12 E1a gene. These re sults suggest that the 13S mRNA product of the Ad12 E1a gene regulates the transcription of its own gene by modulating the activity of TBP.