title: Ancient origin, functional conservation and fast evolution of DNA-dependent RNA polymerase III.
abstract: RNA polymerase III contains seventeen subunits in yeasts (Saccharomyces cerevisiae and Schizosaccharomyces pombe) and in human cells. Twelve of them are akin to the core RNA polymerase I or II. The five other are RNA polymerase III-specific and form the functionally distinct groups Rpc31-Rpc34-Rpc82 and Rpc37-Rpc53. Currently sequenced eukaryotic genomes revealed significant homology to these seventeen subunits in Fungi, Animals, Plants and Amoebozoans. Except for subunit Rpc31, this also extended to the much more distantly related genomes of Alveolates and Excavates, indicating that the complex subunit organization of RNA polymerase III emerged at a very early stage of eukaryotic evolution. The Sch.pombe subunits were expressed in S.cerevisiae null mutants and tested for growth. Ten core subunits showed heterospecific complementation, but the two largest catalytic subunits (Rpc1 and Rpc2) and all five RNA polymerase III-specific subunits (Rpc82, Rpc53, Rpc37, Rpc34 and Rpc31) were non-functional. Three highly conserved RNA polymerase III-specific domains were found in the twelve-subunit core structure. They correspond to the Rpc17-Rpc25 dimer, involved in transcription initiation, to an N-terminal domain of the largest subunit Rpc1 important to anchor Rpc31, Rpc34 and Rpc82, and to a C-terminal domain of Rpc1 that presumably holds Rpc37, Rpc53 and their Rpc11 partner.
authors.affiliation: Laboratory of Mechanisms of Gene Expression, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia.
authors.forename: Galina M
authors.initials: GM
authors.lastname: Proshkina
authors.forename: Elena K
authors.initials: EK
authors.lastname: Shematorova
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Proshkin
authors.forename: Cécile
authors.initials: C
authors.lastname: Zaros
authors.forename: Pierre
authors.initials: P
authors.lastname: Thuriaux
authors.forename: George V
authors.initials: GV
authors.lastname: Shpakovski
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D005816:Genetic Complementation Test; D006801:Humans; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D012320:RNA Polymerase III / Q000737:chemistry / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D012568:Schizosaccharomyces / Q000201:enzymology*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D021122:Protein Subunits; D029702:Schizosaccharomyces pombe Proteins; D012320:RNA Polymerase III