Involvement of DNA gyrase in the transcription of ribosomal RNA

The DNA gyrase inhibitor novobiocin specifically inhibits the transcription of ribosomal RNA in vivo while protein synthesis and the mRNA transcription are only partly affected. In vitro the novobiocin inhibition is only observed when protein fraction, which stimulates ribosomal RNA synthesis, is present. These results indicate that DNA gyrase is involved in the transcription of ribosomal RNA, probably at an initiation step.