title: An Rpb4/Rpb7-like complex in yeast RNA polymerase III contains the orthologue of mammalian CGRP-RCP.
abstract: The essential C17 subunit of yeast RNA polymerase (Pol) III interacts with Brf1, a component of TFIIIB, suggesting a role for C17 in the initiation step of transcription. The protein sequence of C17 (encoded by RPC17) is conserved from yeasts to humans. However, mammalian homologues of C17 (named CGRP-RCP) are known to be involved in a signal transduction pathway related to G protein-coupled receptors, not in transcription. In the present work, we first establish that human CGRP-RCP is the genuine orthologue of C17. CGRP-RCP was found to functionally replace C17 in Deltarpc17 yeast cells; the purified mutant Pol III contained CGRP-RCP and had a decreased specific activity but initiated faithfully. Furthermore, CGRP-RCP was identified by mass spectrometry in a highly purified human Pol III preparation. These results suggest that CGRP-RCP has a dual function in mammals. Next, we demonstrate by genetic and biochemical approaches that C17 forms with C25 (encoded by RPC25) a heterodimer akin to Rpb4/Rpb7 in Pol II. C17 and C25 were found to interact genetically in suppression screens and physically in coimmunopurification and two-hybrid experiments. Sequence analysis and molecular modeling indicated that the C17/C25 heterodimer likely adopts a structure similar to that of the archaeal RpoE/RpoF counterpart of the Rpb4/Rpb7 complex. These RNA polymerase subunits appear to have evolved to meet the distinct requirements of the multiple forms of RNA polymerases.
authors.affiliation: Service de Biochimie et de Génétique Moléculaire, CEA/Saclay, F-91191 Gif sur Yvette Cedex, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Siaut
authors.forename: Cécile
authors.initials: C
authors.lastname: Zaros
authors.forename: Emilie
authors.initials: E
authors.lastname: Levivier
authors.forename: Maria-Laura
authors.initials: ML
authors.lastname: Ferri
authors.forename: Magali
authors.initials: M
authors.lastname: Court
authors.forename: Michel
authors.initials: M
authors.lastname: Werner
authors.forename: Isabelle
authors.initials: I
authors.lastname: Callebaut
authors.forename: Pierre
authors.initials: P
authors.lastname: Thuriaux
authors.forename: André
authors.initials: A
authors.lastname: Sentenac
authors.forename: Christine
authors.initials: C
authors.lastname: Conesa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008322:Mammals; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D012319:RNA Polymerase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012320:RNA Polymerase III / Q000235:genetics / Q000378:metabolism*; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; C108477:CRCP protein, human; C064971:FliA protein, Bacteria; D005656:Fungal Proteins; D046911:Macromolecular Substances; D018015:Receptors, Calcitonin Gene-Related Peptide; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C063202:sporulation-specific sigma factors; D012319:RNA Polymerase II; C423309:RPB4 protein, S cerevisiae; C470553:RPB7 protein, S cerevisiae; D012320:RNA Polymerase III