THE p53 protein is apparently central to the development of human cancers because both alleles are often found to be mutated in different tumour types1. In addition, wild-type p53 can inhibit transformation by viral and cellular oncogenes in vitro, so p53 has been classified as a tumour suppressor2. Investigations of the normal function of p53 have indicated that at least one of its functions could involve the activation of gene expression through the binding of specific DNA-regulatory sequences 3,4. Also, overexpression of p53 can mediate growth arrest 5 and repress transcription from a variety of promoters 6,7. We demonstrate here both in vivo and in vitro that expression of wild-type p53 specifically represses the activity of promoters whose initiation is dependent on the presence of a TAT A box. Promoters whose accurate transcription is directed by a pyrimidine-rich initiator element, however, are immune to the effects of p53. Furthermore, we observe that repression is mediated by an interaction of p53 with basal transcription factor(s). Thus, p53 appears to repress the activity of certain promoters through direct communication with TATA box-dependent basal transcription machinery.
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