Structure of the genes encoding transcription factor IIB and TATA box-binding protein from Drosophila melanogaster

To investigate the structure and regulation of the genes encoding components of the basal RNA polymerase II transcriptional machinery, the Drosophila melanogaster genes encoding transcription factor IIB (TFIIB) and the TATA-box-binding protein (TBP) were isolated and characterized. In the TBP gene, a single intron bisects the sequences that encode the two repeated DNA-binding domains of TBP, which supports the notion that TBP evolved from an earlier form that possessed only a single domain. The transcription start points (tsp) were determined, and there was a good correlation between the tsp that were used in vivo and transcription reactions in vitro. The TFIIB and TBP genes have several similar features, which include high A + T content (68 to 74%) upstream from the tsp, multiple copies of an ATTATTATT sequence motif in the proximal promoter region, the absence of a consensus TATA-box element, and small introns (55 to 64 nucleotides). These genes should be useful in the combined genetic and biochemical analysis of TFIIB and TBP in D. melanogaster.