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 gene comprises distinct elements, TATA and/or initiator (Inr). The existence 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 transcriptional requirements for the TATA-containing, Inr-less (TATA(+)Inr(-)) promoters are different from the transcriptional requirements for the TATA-less, Inr-containing (TATA(-)Inr(+)) promoters. Although both types of promoters require the transcription initiation factor (TFIID) in addition to other common initiation factors, a TATA(-)Inr(+) promoter requires accessory component(s). Here we have employed in vitro analyses to address the transcription factor requirements for a TATA(-)Inr(+) promoter. We demonstrate that in addition to TFIID, a naturally occurring TATA(-)Inr(+-) promoter requires TFII-I, an Inr element-dependent transcription factor. Consistent with its Inr element-dependent activities, TFII-I is dispensable for a TATA(+)Inr(-) promoter. Furthermore, we demonstrate that both TFII-I and TFIID activities in nuclear extracts are temperature-sensitive. However, TFII-I is heat-inactivated at temperatures lower than that required to inactivate TFIID. Therefore, differential heat treatment of nuclear extracts provides an assay to discriminate between transcriptional requirements at TATA(+)Inr(-) and TATA(-)Inr(+) promoters.