title: Inactivation of the SMN complex by oxidative stress.
abstract: The SMN complex is essential for the biogenesis of small nuclear ribonucleoproteins (snRNPs), the major constituents of the spliceosome. Deficiency in functional SMN protein causes spinal muscular atrophy, a common motor neuron degenerative disease of severity commensurate with SMN levels and, correspondingly, snRNP assembly decreases. We developed a high-throughput screen for snRNP assembly modifiers and discovered that reactive oxygen species (ROS) inhibit SMN-complex activity in a dose-dependent manner. ROS-generating compounds, e.g., the environmental toxins menadione and beta-lapachone (in vivo IC(50) = 0.45 muM) also cause intermolecular disulfide crosslinking of SMN. Both the oxidative inactivation and SMN crosslinking can be reversed by reductants. We identified two cysteines that form SMN-SMN disulfide crosslinks, defining specific contact points in oligomeric SMN. Thus, the SMN complex is a redox-sensitive assemblyosome and an ROS target, suggesting that it may play a role in oxidative stress pathophysiology, which is associated with many degenerative diseases.
authors.affiliation: Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Wan
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ottinger
authors.forename: Sungchan
authors.initials: S
authors.lastname: Cho
authors.forename: Gideon
authors.initials: G
authors.lastname: Dreyfuss
mesh_terms: D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009285:Naphthoquinones / Q000737:chemistry / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000494:pharmacology; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D055532:SMN Complex Proteins; D016415:Sequence Alignment; D054852:Small Molecule Libraries / Q000494:pharmacology
chemical_list: D003432:Cross-Linking Reagents; D017362:Cyclic AMP Response Element-Binding Protein; D004220:Disulfides; D009285:Naphthoquinones; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D017382:Reactive Oxygen Species; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; D054852:Small Molecule Libraries; C014638:beta-lapachone; D003545:Cysteine; D004229:Dithiothreitol