title: On the early evolution of RNA polymerase.
abstract: The lines of evidence suggesting that RNA preceded double-stranded DNA as an informational macromolecule are briefly reviewed. RNA polymerase is hypothesized to have been one of the earliest proteins to appear. It is argued that an important vestige of the original enzyme is found in the contemporary eubacterial beta' subunit of DNA-dependent RNA polymerase and its homologues among the archaebacterial and eukaryotic enzymes. The evidence that supports a catalytic role in replicase activity of this polypeptide is reviewed. It is suggested that several characteristics of the Escherichia coli transcriptional apparatus are relatively recent evolutionary developments. The phylogenetic importance of the eubacterial beta' subunit from RNA polymerase and its homologues is emphasized, because it allows the study of the evolutionary relationships of the major cellular lines (eubacteria, archaebacteria, and eukaryotes) as well as of some viral lineages.
authors.affiliation: Departamento de Microbiologia, Escuela Nacional de Ciencias Biológicas, IPN, México, Distrito Federal.
authors.forename: A
authors.initials: A
authors.lastname: Lazcano
authors.forename: J
authors.initials: J
authors.lastname: Fastag
authors.forename: P
authors.initials: P
authors.lastname: Gariglio
authors.forename: C
authors.initials: C
authors.lastname: Ramírez
authors.forename: J
authors.initials: J
authors.lastname: Oró
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D019915:DNA Primase; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D012316:RNA Nucleotidyltransferases / Q000235:genetics; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D046911:Macromolecular Substances; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D012321:DNA-Directed RNA Polymerases