We have isolated and sequenced cDNA clones encoding the human U1-70K snRNP protein, and have mapped this locus (U1AP1) to human chromosome 19. The gene produces two size classes of RNA, a major 1.7-kb RNA and a minor 3.9-kb RNA. The 1.7-kb species appears to be the functional mRNA; the role of the 3.9-kb RNA, which extends further in the 5' direction, is unclear. The actual size of the hU1-70K protein is probably 52 kd, rather than 70 kd. The protein contains three regions similar to known nucleic acid-binding proteins, and it binds RNA in an in vitro assay. Comparison of the cDNA sequences indicates that there are multiple subclasses of mRNA that arise by alternative pre-mRNA splicing of at least four alternative exon segments. This suggests that multiple forms of the hU1-70K protein may exist, possibly with different functions in vivo.

Objective. To evaluate the correlation between the presence of antibodies to an endogenous retroviral element-encoded nuclear protein autoantigen, HRES-1, and the presence of other antinuclear antibodies and HLA class I1 alleles in patients with systemic lupus erythematosus (SLE) and overlap syndromes.Methods. Antibody reactivities to native and recombinant proteins and synthetic peptides were assessed by counterimmunoelectrophoresis, enzyme-linked immunosorbent assay, and Western blotting. HLA class I1 alleles were determined by oligonucleotide typing.Results. significant association between anti-HRES-1 and anti-RNP and an inverse correlation between HRES-1 and RolLa autoantibodies in patients with SLE or overlap syndromes. Antigenic epitopes of HRES-1 and the retroviral gag-related region of the 70-kd protein component of U1 small nuclear RNP, which share 3 consecutive highly charged amino acids (Arg-Arg-Glu), an additional Arg, and functionally similar ArgILys residues, represent cross-reactive epitopes between the two proteins. Selective removal of HRES-1 antibodies from sera of HRES-l-seropositive/RNP-seropositive patients by absorption on recombinant HRES-l/glutathione-Stransferase-conjugated agarose beads had no effect on anti-RNP reactivities. A comparative multivariate analysis of HLA class I1 genes revealed a differential segregation of DQBl alleles in HRES-l-seropositive versus HRES-1-seronegative patients (P = 0.04). While a relative increase of DQB1*0402 among HRES-1-seropositive patients was noted across ethnic groups (P = 0.02), a decrease of DQB1*0201 and DQB1*0301 was found in white HRES-l-seropositive patients (P = 0.04).Conclusion. Autoantibodies to HRES-1 are detectable in a distinct subset of patients with autoimmune disease, primarily in those who do not have antibodies to Ro and La. Anti-HRES-1 and anti-RNP reactivities are mediated by cross-reactive but separate antibody molecules. HLA-DQB genes, rather than HLA-DRB or DQA genes, may have a more significant influence on generation of these antinuclear autoantibodies.A hallmark of the destructive autoimmune process in patients with systemic lupus erythematosus

Objective. To analyze T and B cell reactivity with U small nuclear RNP (snRNP) 70-kd, B, and D polypeptides among patients with connective tissue disease (CTD) and to examine the functional characteristics of snRNP-reactive T cell clones.Methods. We used an snRNP enzyme-linked immunosorbent assay and immunoblotting to characterize antibodies in patients' sera. We used human recombinant fusion proteins 70 kd, B, and D to stimulate and clone snRNP-reactive T cells from CTD patients. We analyzed the cell surface phenotype, antigenic specificity, and cytokine profiles of T cell clones.Results. Patients showed T cell responsiveness to snRNP polypeptides that paralleled their autoantibody reactivities. A total of 256 clones were generated, and clones were identified which were specific for the 70-kd, B, or D polypeptides. Clones expressed a T helper cell phenotype, and were found to produce substantial quantities of both interleukin-4 (IL-4) and interferon-y, and lesser quantities of IL-2 and IL-6.Conclusion. These results show that CTD patients have clonable circulating snRNP-reactive T cells that parallel the specificity of snRNP-reactive antibodies in their sera. The snRNP-reactive T cells exhibit a helper

No abstract