CONNECTING A PROMOTER-BOUND PROTEIN TO TBP BYPASSES THE NEED FOR A TRANSCRIPTIONAL ACTIVATION DOMAIN

BIOCHEMICAL analyses have suggested potential targets for transcriptional activation domains, which include several components of the RNA polymerase II machinery(1-7), as well as the chromatin template(8-12). Here we examine the mechanism of transcriptional activation in yeast cells by connecting a heterologous DNA-binding domain (LexA) to the TATA-binding protein (TBP), LexA-TBP efficiently activates transcription from a promoter containing a LexA operator upstream of a TATA element, Activation is promoter-specific and is sensitive to mutations on the DNA-binding surface of TBP; hence it is not due to a fortuitous activation domain on TBP, Thus a promoter-bound protein lacking an activation domain can stimulate transcription if it is directly connected to TBP. This suggests that recruitment of TBP to the promoter can be a rate-limiting step for transcription in vivo, and that interactions between activation domains and factors that function after TBP recruitment can be bypassed for activation.