Can RNAPolII function as an RNA-dependent RNA-polymerase?
RNA polymerase II (Pol II) is a well-characterized DNA-dependent RNA polymerase, which has also been reported to have RNA-dependent RNA polymerase (RdRP) activity. Pol II can use a homopolymeric RNA template, can extend RNA by several nucleotides in the absence of DNA, and has been implicated in the replication of the RNA genomes of hepatitis delta virus (HDV) and plant viroids. The RdRP activity of Pol II provides a missing link in molecular evolution, because it suggests that Pol II evolved from an ancient replicase that duplicated RNA genomes.