ISOLATION OF A CDNA-ENCODING THE LARGEST SUBUNIT OF TFIIA REVEALS FUNCTIONS IMPORTANT FOR ACTIVATED TRANSCRIPTION

Transcription factor IIA has been shown to interact with the TATA-bind ing protein and to act early during preinitiation complex formation. T he human factor is composed of three subunits (alpha, beta, gamma). A human cDNA clone encoding the largest subunit of TFIIA (alpha) was iso lated. The recombinant alpha polypeptide, together with the beta and g amma subunits, was capable of reconstituting TFIIA activity. Studies u sing antibodies raised against recombinant alpha polypeptide demonstra te that TFIIA can be an integral component of the preinitiation comple x. We demonstrate that TFIIA not only interacts with TBP but also can associate with the TFIID complex. Functional assays establish that TFI IA has no apparent role in basal transcription but plays an important role in activation of transcription. Interestingly, amino acid sequenc e analyses of the beta-subunit demonstrate these residues to be entire ly contained within the carboxyl terminus of the cDNA clone encoding t he alpha-subunit.