Both the rpb9 gene and its cDNA encoding the subunit 9 of RNA polymerase II were cloned from the fission yeast Schizosaccharomyces pombe. From the DNA sequences, Rpb9 was predicted to consist of 113 amino acid residues with a molecular mass of 13,175. S. pombe Rpb9 is 47, 40 and 36% identical in amino acid sequence to the corresponding subunits from Saccharomyces cerevisiae, human and Drosophila melanogaster, respectively. Previously, we failed to detect Rpb9 in the purified RNA polymerase II by amino-terminal micro-sequencing of proteolytic fragments of subunits separated by SDS-gel electrophoresis. After Western blot analysis using antibodies raised against the protein product of the newly isolated rpb9 gene, we found that the purified RNA polymerase II contains Rpb9.