Characterization of the mouse autoantigen La (SS-B). Identification of conserved RNA-binding motifs, a putative ATP binding site and reactivity of recombinant protein with poly(U) and human autoantibodies.
To facilitate the study of autoimmunity to the nuclear Ag La (SS-B) we have isolated and characterized cDNA encoding the mouse La (SS-B) protein. Mouse La (SS-B) protein has 76.7% identity to both human and bovine La (SS-B) proteins and the previously recognized RNP-binding motifs were noted to be highly conserved across the three species. Examination of the primary sequence of human and bovine La (SS-B) newly identifies the site of a potential ATP-binding motif G/AXXXXGK which is preserved in mouse La (SS-B) despite a unique 16 amino acid insertion present in this region of the mouse protein. Analysis of mouse genomic DNA suggests a single gene encodes mouse La (SS-B) and no restriction fragment polymorphisms were identified in the three mouse strains investigated. Two alternate 5' untranslated regions were identified in mouse La (SS-B) cDNA and La (SS-B) mRNA was identified in a wide range of murine tissues consistent with its ubiquitous expression. Recombinant mouse La (SS-B) protein purified from Escherichia coli was shown to bind to poly(U) agarose and to react with sera containing anti-La (SS-B) antibodies obtained from patients with Sjögren's syndrome. The ability to produce recombinant mouse La (SS-B) should provide a valuable reagent for the study of the cellular autoimmune response as well as immunologic tolerance to La (SS-B) Ag in mice.
Topfer
F
F
Department of Clinical Immunology, Flinders Medical Centre, Bedford Park, South Australia.
Gordon
T
T
McCluskey
J
J
D000255:Adenosine Triphosphate / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000818:Animals; D000937:Antigen-Antibody Reactions; D001323:Autoantibodies / Q000737:chemistry*; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D001483:Base Sequence; D002417:Cattle; D017124:Conserved Sequence; D004247:DNA / Q000302:isolation & purification; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011072:Poly U / Q000276:immunology*; D016601:RNA-Binding Proteins / Q000276:immunology / Q000302:isolation & purification*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology*; D012261:Ribonucleoproteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D000097585:SS-B Antigen
D000255:Adenosine Triphosphate; D001323:Autoantibodies; D001324:Autoantigens; D004247:DNA; D011072:Poly U; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D000097585:SS-B Antigen