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Non-canonical DNA transcription enzymes and the conservation of two-barrel RNA polymerases
- Ruprich-Robert, Gwenaël, Thuriaux, Pierre
- Nucleic acids research 2010 v.38 no.14 pp. 4559-4569
- DNA, RNA, active sites, amino acid sequences, amino acids, bacteriophages, enzymes, gene silencing, monophyly, proteins
- 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-Ψ 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.