Molecular identification and characterization of hRPC11, the smallest subunit specific for human RNA polymerase III

Full-length copies of cDNA of the hRPC11 gene encoding the smallest specifi c subunit of nuclear RNA polymerase III were identified among human transcr ipts with the use of the RT-PCR technique. The cloning of the first ortholo gue of the subunit RPC11 from a multicellular organism and the comparison o f subunit hRPC11 of Homo sapiens (108 aa; M-r 12.3 kDa; pI 8.05) deduced fr om the cDNA primary structure with the homologous components of RNA polymer ase Ill from Saccharomyces cerevisiae and Schizosaccharomyces pombe reveale d the most important functional domains: a Zn-binding motif of the classic type (CxxCx(16-17)CxxC) at the N-terminal region, and two extended regions of homology (KEVDDVLGG and RSADEPM) in the central and C-terminal parts of the molecule, respectively. The C-terminus of the RPC11 subunits is highly homologous to the unique zinc ribbon of the elongation factor TFIIS, which suggests a role for this subunit in the elongation or termination of RNA sy nthesis.