MOLECULAR-CLONING OF CDNA-ENCODING THE SMALL-SUBUNIT OF DROSOPHILA TRANSCRIPTION INITIATION-FACTOR TFIIF

Transcription initiation factor TFIIF is a tetramer consisting of two large subunits (TFIIF alpha or RAP74) and two small subunits (TFIIF be ta or RAP30). We report here the molecular cloning of a Drosophila cDN A encoding TFIIF beta. The cDMA clone contains an open-reading frame e ncoding a 277 amino acid polypeptide having a calculated molecular mas s of 32 107 Da. Comparison of the deduced amino acid sequence with the corresponding sequences from vertebrates showed only 50% identity, wi th four insertion/deletion points. For transcription activity in a TFI IF-depleted Drosophila nuclear extract, both TFIIF alpha and TFIIF bet a are essential. Moreover, Drosophila TFIIF beta interacts with both D rosophila and human TFIIF alpha in vitro. Thus we conclude that isolat ed cDNA encodes bona fide TFIIF beta. The structural domains of TFIIF beta and its sequence similarity to bacterial sigma factors are discus sed.