Transcription of native DNA by DNA-dependent RNA polymerases of members of the thermoacidophilic branch of the archaebacteria like that of eukaryotic RNA polymerase A of rat liver, is stimulated by the flavonolignane derivative silybin. Eubacterial RNA polymerases are not affected. For both RNA polymerase A of rat liver and RNA polymerase of Thermoplasma acidophilum the stimulatory effect is confined to the enhancement of the elongation reaction suggesting a similar mechanism for both enzymes. These results further support a specific phylogenetic relationships between the archaebacteria and the eukaryotic cytoplasm.
