Molecular cloning of DNAs encoding the regulatory subunits of elongin from Saccharomyces cerevisiae and Drosophila melanogaster.

The Elongin complex strongly stimulates the rate of elongation by RNA polymerase II by suppressing transient pausing by polymerase at many sites along the DNA. Elongin is composed of a transcriptionally active A subunit and two positive regulatory B and C subunits. The Elongin complex is a potential target for regulation by the von Hippel-Lindau (VHL) tumor suppressor protein, which is capable of binding stably to the Elongin BC complex and preventing it from activating Elongin A. Here, we report the molecular cloning of a Saccharomyces cerevisiae genomic DNA encoding Elongin C subunit and of Drosophila cDNAs encoding Elongin B and C subunits. The predicted amino acid sequence of each protein shows a high degree of similarity with the mammalian proteins. The recombinant yeast Elongin C protein interacts with both mammalian Elongin A and VHL tumor suppressor protein. Moreover, yeast Elongin C strongly induces the transcriptional elongation activity of mammalian Elongin A. The expression of yeast Elongin C mRNA is dramatically upregulated during sporulation; however, the gene is not essential for sporulation and viability in yeast cell.