Structure of the eukaryotic transcription apparatus: features of the gene for the largest subunit of Drosophila RNA polymerase II.

The Drosophila melanogaster RpII215 locus encodes the largest subunit of RNA polymerase II. We have now mapped the 7 kb transcript of the locus and have determined that it contains four exons and three introns. By sequencing 2582 nucleotides from the promoter-proximal end of the RpII215 locus, we have precisely mapped the start site of transcription and the splice sites of the first intron. Segments of the amino acid sequence predicted by the only long open reading frame of the RpII215 gene transcript display striking homology with corresponding segments of the beta subunit of E. coli RNA polymerase.