Nd6p, a novel protein with RCC1-like domains involved in exocytosis in Paramecium tetraurelia.
In Paramecium tetraurelia, the regulated secretory pathway of dense core granules called trichocysts can be altered by mutation and genetically studied. Seventeen nondischarge (ND) genes controlling exocytosis have already been identified by a genetic approach. The site of action of the studied mutations is one of the three compartments, the cytosol, trichocyst, or plasma membrane. The only ND genes cloned to date correspond to mutants affected in the cytosol or in the trichocyst compartment. In this work, we investigated a representative of the third compartment, the plasma membrane, by cloning the ND6 gene. This gene encodes a 1,925-amino-acid protein containing two domains homologous to the regulator of chromosome condensation 1 (RCC1). In parallel, 10 new alleles of the ND6 gene were isolated. Nine of the 12 available mutations mapped in the RCC1-like domains, showing their importance for the Nd6 protein (Nd6p) function. The RCC1 protein is well known for its guanine exchange factor activity towards the small GTPase Ran but also for its involvement in membrane fusion during nuclear envelope assembly. Other proteins with RCC1-like domains are also involved in intracellular membrane fusion, but none has been described yet as involved in exocytosis. The case of Nd6p is thus the first report of such a protein with a documented role in exocytosis.
Gogendeau
Delphine
D
Centre de Génétique Moléculaire, CNRS, 1 avenue de la terrasse, 91198 Gif-sur-Yvette, France. gogendeau@cgm.cnrs-gif.fr
Keller
Anne-Marie
AM
Yanagi
Akira
A
Cohen
Jean
J
Koll
France
F
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D016384:Consensus Sequence; D016054:DNA, Protozoan / Q000032:analysis; D005089:Exocytosis; D020868:Gene Silencing; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames; D016805:Paramecium tetraurelia / Q000737:chemistry* / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000502:physiology
D016054:DNA, Protozoan; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins