title: RNA polymerase I structure and transcription regulation.
abstract: Transcription of ribosomal RNA by RNA polymerase (Pol) I initiates ribosome biogenesis and regulates eukaryotic cell growth. The crystal structure of Pol I from the yeast Saccharomyces cerevisiae at 2.8 Å resolution reveals all 14 subunits of the 590-kilodalton enzyme, and shows differences to Pol II. An 'expander' element occupies the DNA template site and stabilizes an expanded active centre cleft with an unwound bridge helix. A 'connector' element invades the cleft of an adjacent polymerase and stabilizes an inactive polymerase dimer. The connector and expander must detach during Pol I activation to enable transcription initiation and cleft contraction by convergent movement of the polymerase 'core' and 'shelf' modules. Conversion between an inactive expanded and an active contracted polymerase state may generally underlie transcription. Regulatory factors can modulate the core-shelf interface that includes a 'composite' active site for RNA chain initiation, elongation, proofreading and termination.
authors.affiliation: Gene Center and Department of Biochemistry, Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Engel
authors.forename: Sarah
authors.initials: S
authors.lastname: Sainsbury
authors.forename: Alan C
authors.initials: AC
authors.lastname: Cheung
authors.forename: Dirk
authors.initials: D
authors.lastname: Kostrewa
authors.forename: Patrick
authors.initials: P
authors.lastname: Cramer
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005786:Gene Expression Regulation; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012318:RNA Polymerase I / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D019473:Transcription Factors, TFII / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D021122:Protein Subunits; D019473:Transcription Factors, TFII; D012318:RNA Polymerase I; C056604:transcription factor TFIIF