title: A comprehensive interaction map of the human survival of motor neuron (SMN) complex.
abstract: Assembly of the Sm-class of U-rich small nuclear ribonucleoprotein particles (U snRNPs) is a process facilitated by the macromolecular survival of motor neuron (SMN) complex. This entity promotes the binding of a set of factors, termed LSm/Sm proteins, onto snRNA to form the core structure of these particles. Nine factors, including the SMN protein, the product of the spinal muscular atrophy (SMA) disease gene, Gemins 2-8 and unrip have been identified as the major components of the SMN complex. So far, however, only little is known about the architecture of this complex and the contribution of individual components to its function. Here, we present a comprehensive interaction map of all core components of the SMN complex based upon in vivo and in vitro methods. Our studies reveal a modular composition of the SMN complex with the three proteins SMN, Gemin8, and Gemin7 in its center. Onto this central building block the other components are bound via multiple interactions. Furthermore, by employing a novel assay, we were able to reconstitute the SMN complex from individual components and confirm the interaction map. Interestingly, SMN protein carrying an SMA-causing mutation was severely impaired in formation of the SMN complex. Finally, we show that the peripheral component Gemin5 contributes an essential activity to the SMN complex, most likely the transfer of Sm proteins onto the U snRNA. Collectively, the data presented here provide a basis for the detailed mechanistic and structural analysis of the assembly machinery of U snRNPs.
authors.affiliation: Theodor-Boveri Institute at the Biocenter, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Otter
authors.forename: Matthias
authors.initials: M
authors.lastname: Grimmler
authors.forename: Nils
authors.initials: N
authors.lastname: Neuenkirchen
authors.forename: Ashwin
authors.initials: A
authors.lastname: Chari
authors.forename: Albert
authors.initials: A
authors.lastname: Sickmann
authors.forename: Utz
authors.initials: U
authors.lastname: Fischer
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000235:genetics; D002474:Cell-Free System / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D009046:Motor Neurons / Q000737:chemistry / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009134:Muscular Atrophy, Spinal / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D017411:Ribonucleoproteins, Small Nuclear; C510132:GEMIN8 protein, human; C466231:GEMIN7 protein, human