Cloning and identification of the gene coding for the 140-kd subunit of Drosophila RNA polymerase II.

Genomic clones of Drosophila melanogaster were isolated from a lambda library by cross-hybridization with the yeast gene coding for the 150-kd subunit of RNA polymerase II. Clones containing a region of approximately 2.0 kb with strong homology to the yeast gene were shown to code for a 3.9-kb poly(A)-RNA. Part of the coding region was cloned into an expression vector. A fusion protein was obtained which reacted with an antibody directed against RNA polymerase II of Drosophila. Peptide mapping of the fusion protein yielded a number of spots identical with spots derived from the 140-kd subunit of Drosophila RNA polymerase II. Sequence comparison of a segment of the Drosophila and the corresponding yeast clone yielded a high degree of homology at the protein level also, suggesting that we had isolated the gene coding for the 140-kd subunit of RNA polymerase II from Drosophila. In situ hybridization localized the DmRP140 gene at 88 A/B on chromosome 3 while the DmRP215 gene has previously been localized at 10 C on the X chromosome. Analysis of the transcripts (7.0 and 3.9 kb) in female and male flies shows dosage compensation for the transcription of the DmRP215 gene.