| description | Protein of the DNA-directed RNA polymerase complexes, which catalyze RNA synthesis the by addition of ribonucleotide units to a RNA chain using DNA as a template. They can initiate a chain de novo Prokaryotes have a single enzyme for the three RNA types that is subject to stringent regulatory mechanisms. Eukaryotes have type I that synthesizes all rRNA except the 5S component, type II that synthesizes mRNA and hnRNA and type III that synthesizes tRNA and the 5S component of rRNA |
