title: Non-canonical DNA transcription enzymes and the conservation of two-barrel RNA polymerases.
abstract: DNA transcription depends on multimeric RNA polymerases that are exceptionally conserved in all cellular organisms, with an active site region of >500 amino acids mainly harboured by their Rpb1 and Rpb2 subunits. Together with the distantly related eukaryotic RNA-dependent polymerases involved in gene silencing, they form a monophyletic family of ribonucleotide polymerases with a similarly organized active site region based on two double-Psi barrels. Recent viral and phage genome sequencing have added a surprising variety of putative nucleotide polymerases to this protein family. These proteins have highly divergent subunit composition and amino acid sequences, but always contain eight invariant amino acids forming a universally conserved catalytic site shared by all members of the two-barrel protein family. Moreover, the highly conserved 'funnel' and 'switch 2' components of the active site region are shared by all putative DNA-dependent RNA polymerases and may thus determine their capacity to transcribe double-stranded DNA templates.
authors.affiliation: CEA, iBiTec-S, Service de Biologie Intégrative et Génétique Moléculaire, Gif-sur-Yvette, France.
authors.forename: Gwenaël
authors.initials: G
authors.lastname: Ruprich-Robert
authors.forename: Pierre
authors.initials: P
authors.lastname: Thuriaux
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001435:Bacteriophages / Q000201:enzymology; D020134:Catalytic Domain; D017124:Conserved Sequence; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism; D007304:Insect Viruses / Q000201:enzymology; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry; D015003:Yeasts / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases