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 (TFllFα or RAP74) and two small subunits (TFIIFβ or RAP30). We report here the molecular cloning of a Drosophila cDNA encoding TFIIFβ. The cDNA clone contains an open-reading frame encoding a 277 amlno acid polypeptlde having a calculated molecular mass of 32107 Da. Comparison of the deduced amino acid sequence with the corresponding sequences from vertebrates showed only 50% identity, with four insertion/deletion points. For transcription activity in a TFIIF-depleted Drosophila nuclear extract, both TFllFα and TFIIFβ are essential. Moreover, Drosophila TFIIFp interacts with both Drosophila and human TFllFα in vitro Thus we conclude that Isolated cDNA encodes bona fide TFIIFβ. The structural domains of TFIIFβ and its sequence similarity to bacterial a factors are discussed.