Cloning of a Drosophila cDNA with sequence similarity to human transcription factor RAP74

Factor 5 is a Drosophila RNA polymerase II initiation factor which also affects the elongation phase of transcription. Drosophila factor 5 and its mammalian counterpart, RAP30/74 (also known as TFIIF or ( beta gamma ), have similar biochemical properties including: 1) their requirement for initiation, 2) the ability to stimulate elongation, 3) a high affinity for purified RNA polymerase II, 4) similar chromatographic properties, and 5) a similar subunit composition. Recently, the sequence of a cDNA coding for RAP74 and the large subunit of TFIIF have been reported. We have used the RAP74 cDNA to isolate a Drosophila cDNA with sequence similarity. When a Drosophila K sub(c) cell cDNA library was probed at low stringency with the cDNA encoding RAP74, a 1.1 kb cDNA with sequence similarity to the 5' end of RAP74 was isolated. The K sub(c) cell cDNA was used to screen a Drosophila) embryonic cDNA library and a larger (1929 bp) cDNA with similarity to the entire RAP74 DNA sequence was isolated. This clone encodes a 577 amino acid protein that is 43% identical and 65% similar to human RAP74.