The rpb10 cDNA of the fission yeast Schizosaccharomyces pombe, encoding one of the five small subunits common to all three nuclear DNA-dependent RNA polymerases, was isolated from an expression cDNA library by two independent approaches: PCR-based screening and direct suppression by means of heterospecific complementation of a temperature-sensitive mutant defective in the corresponding gene of Saccharomyces cerevisiae. The cloned Sz. pombe cDNA encodes a protein Rpb10 of 71 amino acids with an M of 8275 Da, sharing 51 amino acids (71% identity) with the subunit ABC10β of RNA polymerases I-III from S. cerevisiae. All eukaryotic members of this protein family have the same general organization featuring two highly conserved motifs (RCFT/SCGK and RYCCRRM) around an atypical zinc finger and an additional invariant HVDLIEK motif toward the C-terminal end. The last motif is only characteristic for homologs from eukaryotes. In keeping with this remarkable structural conservation, the Sz. pombe cDNA also fully complemented a S. cerevisiae deletion mutant lacking subunit ABC10β (null allele rpb10-Δl::HlS3). © 1997 MAEe cyrillic signK Hayκa/Interperiodica Publishing.