CORE PROMOTER-SPECIFIC FUNCTION OF A MUTANT TRANSCRIPTION FACTOR TFIID DEFECTIVE IN TATA-BOX BINDING

In conjunction with other general initiation factors, the TATA box-bin ding protein (TBP) can direct basal transcription by RNA polymerase II from TATA-containing promoters, but its stable interaction with TBP-a ssociated factors (TAFs) in the TFIID complex is required both for act ivator-dependent transcription and for basal transcription directed by an initiator element. We have generated a TATA-binding-defective TFII D complex containing an amino acid substitution in the DNA-binding sur face of its TBP subunit, This mutated TFIID is defective in both basal and activated transcription from core promoters containing only a TAT A box but supports transcription from initiator-containing promoters i ndependently of the presence or absence of a TATA sequence. Our result s show that a functional initiator element is needed to bypass the req uirement for an active TATA DNA-binding surface in TFIID and imply tha t gene-specific transcription can be achieved by modulating distinct c ore promoter-specific TFIID functions-e.g., TBP-TATA versus TAF-initia tor interactions.