RNA Polymerase III, DNA Directed Polypeptide K (POLR3K)

POLR3K encodes a small essential subunit of RNA polymerase III, the polymerase responsible for synthesizing transfer and small ribosomal RNAs in eukaryotes. The carboxy-terminal domain of this subunit shares a high degree of sequence similarity to the carboxy-terminal domain of an RNA polymerase II elongation factor. This similarity in sequence is supported by functional studies showing that this subunit is required for proper pausing and termination during transcription. The deduced 108-amino acid protein contains N- and C-terminal zinc-binding motifs and an intermediate domain with a conserved 9-residue sequence (KEVDDVLGG). Each domain is encoded by a separate exon in the human gene. The C-terminal zinc-binding motif is 67% similar to the zinc ribbon of TFIIS.