is synthesized. The domain organization and the 3D structure of the catalytic centre of a wide range of RdRps, even those with a low overall sequence homology, are conserved. The catalytic center is formed by several motifs containing conserved amino acid residues.

Eukaryotic RNA interference requires a cellular RdRp (c RdRp). Unlike the "hand" polymerases, they resemble simplified multi-subunit DdRPs, specifically in the catalytic ?/?' subunits, in that they use two sets of double-psi ?-barrels