A TATA SEQUENCE-DEPENDENT TRANSCRIPTIONAL REPRESSOR ACTIVITY ASSOCIATED WITH MAMMALIAN TRANSCRIPTION FACTOR IIA

In the process of characterizing cellular proteins that modulate basal transcription by RNA polymerase II, we identified a novel repressor activity specific for promoters containing consensus TATA boxes. This activity strongly represses TATA-binding protein (TBP)-dependent transcription initiation from core promoter elements containing a consensus TATA sequence, but activates TBP-dependent transcription from core promoter elements lacking a consensus TATA sequence. Purification of this activity to near homogeneity from rat liver nuclear extracts led to the surprising discovery that it co-purifies closely with mammalian transcription factor IIA (TFIIA). The close association of TATA sequence-dependent transcriptional repressor activity with TFIIA adds a new and unexpected dimension to the already complex picture of this factor's function in transcription by RNA polymerase II.