Institut für Molekulare Genetik, Universität Heidelberg, F.R.G.
To analyze the transcriptional control regions of Drosophila melanogaster household genes, we have characterized the promoter of the gene coding for the second-largest subunit of RNA polymerase II (DmRP140). Analysis of cDNA revealed that the coding region of the protein extends beyond the originally assumed transcription start point (tsp) and deduced translation start codon [Falkenburg et al., J. Mol. Biol. 195 (1987) 929-937] and that the tsp determined previously corresponds to an intron/exon boundary of an additional intron. Upstream of the polII gene we found a transcription unit that is transcribed in the opposite direction. The initiating ATGs of the two genes are only 467 nucleotides (nt) apart. The untranslated region is extremely A + T-rich (88%) but none of the transcription units is preceded by a canonical TATA element. It does not feature any other known nt sequence motifs thought to be necessary for the basic transcriptional machinery; yet, this region functions as a bidirectional promoter: a central 309-bp fragment directs transcription of a reporter gene in transiently transfected Drosophila culture cells in both orientations. The gene coding for the second-largest subunit of RNA polymerase II of Drosophila virilis (DvRP140) was isolated and partially analyzed. The gene is located on the second chromosome at 22F/23A which corresponds to the position determined for D. melanogaster.(ABSTRACT TRUNCATED AT 250 WORDS)