TFII IS REQUIRED FOR TRANSCRIPTION OF THE NATURALLY TATA-LESS BUT INITIATOR-CONTAINING V-BETA PROMOTER

The proximal or core promoter of a typical eukaryotic protein coding g ene comprises distinct elements, TATA and/or initiator (Inr). The exis tence of TATA or Inr at the core promoter suggests that the mechanism of transcription initiation mediated by these two genetic elements may be different. Accordingly, it has been demon strated that the transcr iptional requirements for the TATA-containing, Inr-less (TATA(+)Inr(-) ) promoters are different from the transcriptional requirements for th e TATA-less, Inr-containing (TATA(-)Inr(+)) promoters. Although both t ypes of promoters require the transcription initiation factor (TFIID) in addition to other common initiation factors, a TATA(-)Inr(+) promot er requires accessory component(s). Here we have employed in vitro ana lyses to address the transcription factor requirements for a TATA(-)In r(+) promoter. We demonstrate that in addition to TFIID, a naturally o ccurring TATA(-)Inr(+-) promoter requires TFII-I, an Inr element-depen dent transcription factor. Consistent with its Inr element-dependent a ctivities, TFII-I is dispensable for a TATA(+)Inr(-) promoter. Further more, we demonstrate that both TFII-I and TFIID activities in nuclear extracts are temperature-sensitive. However, TFII-I is heat-inactivate d at temperatures lower than that required to inactivate TFIID. Theref ore, differential heat treatment of nuclear extracts provides an assay to discriminate between transcriptional requirements at TATA(+)Inr(-) and TATA(-)Inr(+) promoters.