Analysis of the structure and expression fo the TFIIB gene in Drosophila melanogaster.

We have isolated and characterized a genomic clone encoding the Drosophila melanogaster transcription factor IIB (TFIIB). The coding region of the TFIIB gene is interrupted by three short introns. The 5'-flanking region of the gene lacks the typical TATA box sequence like those of other known genes encoding the general transcription factors. In addition, the 5'-flanking region of the gene contains several common DNA sequences present in Drosophila TBP and TFIIS genes, suggesting the common regulation mechanism of gene expression. RNA blot analysis revealed that the gene expresses 1.6 kb, 1.3 kb and 1.2 kb mRNAs throughout development and in adults. Deletion analysis of the promoter region shows that the minimal promoter necessary for efficient expression is located between -698 (PstI) and +60 relative to the transcription start point. Within this minimal promoter region, the upstream regulatory element responsible for the stimulation of gene expression may exist in the DNA fragment between -698 (PsfI) and -351 (StuI).