Novel autoantibodies directed against the common tertiary configuration of transfer RNA in a patient with interstitial lung disease

Objective. To identify and characterize a novel autoantibody, anti‐WS, that binds total transfer RNA (tRNA). Methods. Serum from patient WS, who had polyarthritis, Sjögren's syndrome, Raynaud's phenomenon, and interstitial pulmonary fibrosis, was used in this study. Characteristics of anti‐WS and antibody‐reactive determinants of tRNA were investigated by 32P immuno‐precipitation using HeLa cell RNA and deletion mutants of tRNA transcribed in vitro. Results. WS serum produced nucleolar and cytoplasmic staining on indirect immunofluorescence. 32P immunoprecipitation assays demonstrated that this serum immunoprecipitated total tRNAs and 5.8S and 5S ribosomal RNAs from 32P‐labeled HeLa cell extract. When deproteinized RNA was used as antigen source, total tRNAs were still precipitated by WS serum. An immunoprecipitation study, using various deletion mutants of Escherichia coli tRNA, demonstrated that both D and T Ψ C loops were needed for antibody binding. Substitution of nucleotide 18G with 18A of E coli tRNA T rp, which is essential in the formation of the tertiary “L” shape of tRNA, inhibited binding by anti‐WS antibodies. Conclusion. Anti‐WS antibodies are novel auto‐antibodies directed against tRNAs. The antibody binding site is the common L‐shaped tertiary structure conformed by the D loop and T Ψ C loop of tRNA, suggesting that the antibodies are induced by a conserved sequence among all species. Furthermore, these antibodies could be a marker for a newly recognized subset of connective tissue disease.