Thirteen Anti-Sm Monoclonal Antibodies Immunoprecipitate the Three Cytoplasmic snRNP Core Protein Precursors in Six Distinct Subsets

The small nuclear ribonucleoprotein particle (snRNP) common core proteins are the lupus-associated Sm autoantigens. In mouse fibroblasts the seven snRNP core proteins form a particle with a suggested stoichiometry of B2[D1,D2(E,F,G)2] D3. Core particle assembly occurs in the cytoplasm where newly sy...

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Bibliographic Details
Published in:Journal of autoimmunity 1999-03, Vol.12 (2), p.91-100
Main Authors: Fury, Matthew, Andersen, Janet, Ponda, Prashant, Aimes, Ronald, Zieve, Gary W.
Format: Article
Language:English
Subjects:
Animals
Antibodies, Monoclonal
Autoantigens - chemistry
Biological and medical sciences
General aspects
HeLa Cells
Humans
Immunoblotting
Immunopathology
L Cells (Cell Line)
Macromolecular Substances
Medical sciences
Mice
Precipitin Tests
Protein Precursors - chemistry
Protein Precursors - immunology
ribonucleoprotein, Sm, snRNP particles, systemic lupus erythematosus
Ribonucleoproteins, Small Nuclear - chemistry
Ribonucleoproteins, Small Nuclear - immunology
snRNP Core Proteins
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Summary:The small nuclear ribonucleoprotein particle (snRNP) common core proteins are the lupus-associated Sm autoantigens. In mouse fibroblasts the seven snRNP core proteins form a particle with a suggested stoichiometry of B2[D1,D2(E,F,G)2] D3. Core particle assembly occurs in the cytoplasm where newly synthesized snRNAs assemble with core proteins stored in three RNA-free complexes of (1) a 6S complex of [D1,D2(E,F,G)2] (2) a 20S complex of (B,D3 and an unidentified 70kDa protein) and (3) a 2S–6S complex that minimally contains the B protein. In this report a panel of 13 anti-Sm monoclonal antibodies is shown to immunoprecipitate six different subsets of the cytoplasmic snRNP proteins. Four epitopes are shared by the three aforementioned complexes and five other epitopes are shared by two of the complexes. In addition, the 6S or 20S complexes are apparently disrupted by five of the antibodies. Kinetic studies show that the three cytoplasmic snRNP protein complexes have independent half-lives. These studies provide another approach for characterizing the Sm epitopes. They also complement previousin vitrosnRNP assembly studies and suggest that snRNP core assembly occurs by the initial binding of snRNA to the 6S particle followed by addition of the B and D3 proteins.
ISSN:0896-8411
1095-9157
DOI:10.1006/jaut.1998.0266