Multisubunit RNA polymerases.

Transcription of the genetic information in all cells is carried out by multisubunit RNA polymerases (RNAPs). Comparison of the crystal structures of a bacterial and a eukaryotic RNAP reveals a conserved core that comprises the active site and a multifunctional clamp. Together with a further structure of eukaryotic RNAP bound to DNA and RNA, these results elucidate many aspects of the transcription mechanism, including initiation, elongation, nucleotide addition, processivity and proofreading.