The SMN-SIP1 complex has an essential role in spliceosomal snRNP biogenesis.
Spinal muscular atrophy (SMA) is an often fatal neuromuscular disease that has been directly linked to the protein product of the Survival of Motor Neurons (SMN) gene. The SMN protein is tightly associated with a novel protein, SIP1, and together they form a complex with several spliceosomal snRNP proteins. Here we show that the SMN-SIP1 complex is associated with spliceosomal snRNAs U1 and U5 in the cytoplasm of Xenopus oocytes. Antibodies directed against the SMN-SIP1 complex strongly interfere with the cytoplasmic assembly of the common (Sm) snRNP proteins with spliceosomal snRNAs and with the import of the snRNP complex into the nucleus. Thus, the SMN-SIP1 complex is directly involved in the biogenesis of spliceosomal snRNPs. Defects in spliceosomal snRNP biogenesis may, therefore, be the cause of SMA.
Fischer
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U
Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104-6148, USA.
Liu
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Q
Dreyfuss
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G
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001692:Biological Transport / Q000235:genetics; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein; D003593:Cytoplasm / Q000737:chemistry; D008845:Microinjections; D009046:Motor Neurons / Q000737:chemistry / Q000502:physiology; D009134:Muscular Atrophy, Spinal / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism / Q000493:pharmacokinetics* / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D010641:Phenotype; D011485:Protein Binding / Q000502:physiology; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear / Q000096:biosynthesis* / Q000378:metabolism; D055532:SMN Complex Proteins; D017381:Spliceosomes / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D017362:Cyclic AMP Response Element-Binding Protein; C108381:GEMIN2 protein, human; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins