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  • The EMBO Journal (2002) 21, 4136 - 4144
  • doi:10.1093/emboj/cdf392

Localization of the yeast RNA polymerase I-specific subunits

Nicolas Bischler1,2, Laurent Brino1,2, Christophe Carles3, Michel Riva3, Herbert Tschochner4, Véronique Mallouh1,2 and Patrick Schultz1,2

  1. Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, 1 rue Laurent Fries, BP163, F-67404 Illkirch Cedex, C.U. de Strasbourg, France
  2. Ecole Supérieure de Biotechnologie de Strasbourg, Pôle API, 1 rue Sébastien Brandt, F-67400 Illkirch, France
  3. Service de Biochimie et de Génétique Moléculaire, CEA/Saclay, F-91191 Gif sur Yvette Cedex, France
  4. Biochemie-Zentrum Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany

Correspondence to:

Patrick Schultz, E-mail: pat@moorea.u-strasbg.fr

Received 3 December 2001; Accepted 3 June 2002; Revised 28 May 2002

The spatial distribution of four subunits specifically associated to the yeast DNA-dependent RNA polymerase I (RNA pol I) was studied by electron microscopy. A structural model of the native enzyme was determined by cryo-electron microscopy from isolated molecules and was compared with the atomic structure of RNA pol II Delta4/7, which lacks the specific polypeptides. The two models were aligned and a difference map revealed four additional protein densities present in RNA pol I, which were characterized by immunolabelling. A protruding protein density named stalk was found to contain the RNA pol I-specific subunits A43 and A14. The docking with the atomic structure showed that the stalk protruded from the structure at the same site as the C-terminal domain (CTD) of the largest subunit of RNA pol II. Subunit A49 was placed on top of the clamp whereas subunit A34.5 bound at the entrance of the DNA binding cleft, where it could contact the downstream DNA. The location of the RNA pol I-specific subunits is correlated with their biological activity.

  • Keywords:

    • atomic structure docking,
    • cryo-electron microscopy,
    • epitope localization,
    • immunolabelling,
    • yeast RNA polymerase I (A)