Activity of the upstream TATA-less promoter of the p21Waf1/Cip1 gene depends on transcription factor IIA (TFIIA) in addition to TFIIA-reactive TBP-like protein

TATA-binding protein-like protein (TLP) binds to transcription factor IIA (TFIIA) with high affinity, although the significance of this binding is poorly understood. In this study, we investigated the role of TFIIA in transcriptional regulation of the p21(Waf1/Cip1) (p21) gene. It has been shown that TLP is indispensable for p53-activated transcription from an upstream TATA-less promoter of the p21 gene. We found that mutant TLPs having decreased TFIIA-binding ability exhibited weakened transcriptional activation function for the upstream promoter. Activity of the upstream promoter was enhanced considerably by an increased amount of TFIIA in a p53-dependent manner, whereas activity of the TATA-containing downstream promoter was enhanced only slightly. TFIIA potentiated the upstream promoter additively with TLP. Although TFIIA is recruited to both promoters, activity of the upstream promoter was much more dependent on TFIIA. Recruitment of TFIIA and TLP to the upstream promoter was augmented in etoposide-treated cells, in which the amount of TFIIA-TLP complex is increased, and TFIIA-reactive TLP was required for the recruitment of both factors. It was confirmed that etoposide-stimulated transcription depends on TLP. We also found that TFIIA-reactive TLP acts to decrease cell growth rate, which can be explained by interaction of the p21 promoter with the transcription factors that we examined. The results of the present study suggest that the upstream TATA-less promoter of p21 needs TFIIA and TFIIA-reactive TLP for p53-dependent transcriptional enhancement.