The cDNAs and genes encoding the common subunits Rpc19 and Rpc40 of nuclear RNA polymerases I and III of Schizosaccharomyces pombe were isolated from cDNA and genomic libraries of the fission yeast and tested for their ability to substitute for the homologous genes in Saccharomyces cerevisiae by heterospecific complementation of corresponding null alleles and temperature-sensitive mutations. The results obtained indicate that both Sz. pombe genes (rpcl9+and rpc40+) are able to replace their S. cerevisiae counterparts in vivo. The primary structure and general organization of both genes were established: rpc40+is an intronless gene, while rpc19+contains three introns (73, 48 and 77 bp long); rpc19+is situated on the long arm of chromosome I and rpc40+on the long arm of chromosome II.