Two small RNAs encoded by Epstein-Barr virus and complexed with protein are precipitated by antibodies from patients with systemic lupus erythematosus

Myositis autoantibody inhibits histidyl-tRNA synthetase: a model for autoimmunity

In autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus (SLE), autoantibodies are generated against a variety of macromolecules. Myositis is a human autoimmune disease characterized by weakness and wasting of muscle. In American studies, antibodies directed against soluble cellular constituents were detected by immunodiffusion in about 60% of cases; the commonest of these, found in 25% of patients, was antibody to the Jo-1 antigen. An antibody system referred to as PL-1 was recognized at a similar frequency in a series of patients studied at Hammersmith Hospital, London. We show here that this system is identical with the Jo-1 system and demonstrate that the antigen is a polypeptide of molecular weight (Mr) 50,000. The protein is immunoprecipitated with tRNA His and appears to be histidyl-tRNA synthetase. The identity of the Jo-1 antigen, the first of the RNA-associated antigens familiar in autoimmune disease to be characterized as a specific enzyme, suggests a model for virus involvement in autoantibody generation.

Characterization of a phosphoprotein associated with the SS-B/La nuclear antigen in adenovirus-infected and uninfected KB cells

We have employed sera from patients with autoimmune disease to characterize the nuclear SS-B/La antigen in uninfected and adenovirus-infected KB cells. A 45,000-dalton phosphorylated polypeptide was specifically precipitated with anti-SS-B sera, and the level of phosphorylation was increased after infection. The increased phosphorylation appears to occur at the same amino acid residues phosphorylated in uninfected cells and results from increased phosphorylating activity rather than from altered enzyme specificity. A competition experiment between infected and uninfected cell extracts indicates that the antigen in the infected cell binds more strongly to SS-B/La antibodies. Fragments of adenovirus-induced virus-associated RNA as well as intact molecules complex with SS-B/La antigen and are immune precipitated with autoimmune sera.

Clinical and biologic significance of antibodies to Ro/SSA

Study of the clinical associations of antibodies to the soluble antigens Ro/SSA and La/SSB leads to several conclusions. Production of such antibodies are linked to the D locus antigens DR2 and DR3, suggesting involvement of disease susceptibility or immune response genes in the regulation of their synthesis. Genetics therefore provides one of the factors that contribute to the disease expression and the clinical heterogeneity that characterize systemic lupus erythematosus (SLE). The uniform presence of anti-Ro/SSA in neonatal lupus and the almost uniform presence of these antibodies in the vasculitis of Sjögren's syndrome suggest the participation of these antibodies in the immunopathogenesis of these particular clinical manifestations. Finally, identification of the molecular nature of these antigens as RNA-protein conjugates and the ability of the antibodies to La/SSB to bind viral-specific RNA-protein conjugates provide clues that may lead to elucidation of etiologic events in the development of SLE.

Characterization of the SS-B (La) antigen in adenovirus-infected and uninfected HeLa cells

The molecular composition and subcellular localization of the antigens recognized by anti-SS-B (La or Ha) antibodies was investigated. Ten anti-SS-B sera were selected by indirect immunofluorescence and by their immunological identity in counter-immunoelectrophoresis (CIE) with an anti-SS-B reference serum. All sera precipitated virus-associated (VA) RNA from cellular extracts of adenovirus-infected HeLa cells. Earlier results had shown that in adenovirus-infected HeLa cells a cellular 50 000 mol. wt. protein was tightly associated with VA RNA in situ. Our present results indicate that this 50 000 protein is the only SS-B antigen present in adenovirus-infected as well as in uninfected cells. A major part (greater than 80%) of the SS-B antigen is present in a readily extractable, soluble form. The rest is found in an insoluble form tightly associated with an internal nuclear structure that is mostly referred to as the nuclear matrix. Both forms are very susceptible to proteolytic degradation resulting in at least two distinct breakdown products of mol. wts. 40 000 and 25 000. The cellular 50 000 polypeptide is present in extracts of various types of cells and tissues, indicating that this antigen is very well conserved during evolution. The association of the 50 000 mol. wt. antigen with host- as well as viral-coded RNA polymerase III products also suggests an important function for this protein in the metabolism of these small RNAs.

Molecular characterization of ribonucleoprotein antigens bound by antinuclear antibodies. A diagnostic evaluation

The specificity of antinuclear antibodies in sera from 54 patients with various rheumatic diseases was analyzed by immunoprecipitation of 32P- or 35S-methionine-labeled HeLa cell extracts. Of 35 sera giving a speckled and/or homogeneous immunofluorescence pattern in rat liver nuclei, 20 contained antibodies to nuclear ribonucleoproteins, which are defined by their ribonucleic acid and protein components. Four sera reacted with a nuclear antigen (Ga) which has not been described so far. Of 19 sera with antinucleolar antibodies, 18 did not react with nuclear or nucleolar ribonucleoproteins. Correlation of these molecularly defined antinuclear antibody specificities with immunofluorescence patterns and rheumatic diseases is discussed.

Interaction between VA RNA and the lupus antigen La: formation of a ribonucleoprotein particle in vitro

The small adenovirus-encoded VA RNAs occur as ribonucleoprotein (RNP) particles in association with a cellular protein antigen, La, recognized by the anti-La class of lupus sera [Lerner, M. R., Boyle, J. A., Hardin, J. A. & Steitz, J. A. (1981) Science 211, 400-402]. We have tentatively identified the La antigen as a HeLa cell phosphoprotein of Mr approximately equal to 45,000, present in infected and uninfected cells. The antigen appears not to be required for the transcription of VA RNAs in vitro. RNP particles that contain newly synthesized VA RNAs assemble rapidly in transcription extracts making VA RNA and also can be reconstituted from purified VA RNA and a source of La antigen. Variant forms of VA RNAI with sequence deletions and substitutions bind to the La antigen, suggesting that the recognition site includes the RNA termini or the sequences corresponding to the internal control region (promoter), or both. Upon reconstitution with fragments of VA RNAI, oligonucleotides from both the 5' and 3' termini bind to the antigen, but those from the control region do not. The terminal oligonucleotides of wild-type VA RNA can form a basepaired stem, but structures of comparable stability cannot be formed by the chimeric variant molecules. Therefore, the recognition site is probably the terminal nucleotides themselves rather than the stem structure.

Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells

Small ribonucleic acid (RNA)-protein complexes precipitated by anti-Ro and anti-La antibodies from lupus patients have been examined with emphasis on their RNA components. In both ribonucleoprotein (RNP) classes, the numbers of different RNA molecules and their sequences vary between mouse and human cells. The complex mixtures of La RNAs include two previously sequenced 4.5S RNAs from mouse cells and 5S ribosomal RNA-like molecules from both mouse and human cells. All Ro and La RNAs possess 5-triphosphates. Some La RNAs have internal modifications typical of transfer RNAs. The Ro RNPs are quite stable and are localized by immunofluorescence in the cell cytoplasm, whereas the majority of the La RNPs turn over rapidly and reside in the nucleus. Despite these differences, reconstitution experiments show that the Ro particles carry the La as well as the Ro determinant. Studies using a nuclear transcription system demonstrate that most of the La RNAs are synthesized by RNA polymerase III. The possibility that the La protein(s) functions in the transcription or maturation of all RNA polymerase III transcripts is discussed.

Epstein-Barr virus RNA. VIII. Viral RNA in permissively infected B95-8 cells

More than 50 RNAs expressed by Epstein-Barr virus late in productive infection have been identified. B95-8-infected cells were induced to a relatively high level of permissive infection with the tumor promotor 12-O-tetradecanoylphorbol-13-acetate. Polyadenylated RNAs were extracted from the cell cytoplasm, separated by size on formaldehyde gels, transferred to nitrocellulose, and hybridized to labeled recombinant Epstein-Barr virus DNA fragments. Comparison of RNAs from induced cultures with RNAs from induced cultures also treated with phosphonoacetic acid to inhibit viral DNA synthesis identifies two RNA classes: a persistent early class of RNAs whose abundance is relatively resistant to viral DNA synthesis inhibition and a late class of RNAs whose abundance is relatively sensitive to viral DNA synthesis inhibition. The persistent early and late RNAs are not clustered but are intermixed and scattered through most of segments UL and US. The cytoplasmic polyadenylated RNAs expressed during latent infection were not detected in productively infected cells, indicating that different classes of viral RNA are associated with latent and productive infection. Non-polyadenylated small RNAs originally identified in cells latently infected with Epstein-Barr virus are expressed in greater abundance in productively infected cells and are part of the early RNA class.

In vitro transcription of two Epstein-Barr virus specified small RNA molecules

Cloned DNA from the EcoRI J fragment of EBV has been used as template for in vitro transcription experiments using cell-free extracts prepared from HeLa or KB cells. Two EBV specific RNAs each about 175 bases in length were synthesised and nuclease 51 mapping experiments determined that these in vitro products corresponded precisely to the in vivo species obtained from Raji cells. These two RNA molecules are transcribed by RNA polymerase III and in common with other pol III-synthesised RNAs the coding sequences contain intragenic control regions. The relative abundance of the two RNAs synthesised in vitro differs from that observed in vivo.

Clinical and serological differences between systemic lupus erythematosus patients with antibodies to Ro versus patients with antibodies to Ro and La

Among 55 systemic lupus erythematosus patients having antibodies to Ro and/or La, two major groups were distinguished by titration of sera in counterimmunoelectrophoresis. The first group (30 patients) had antibodies to Ro alone. This was associated with a high incidence of antibodies to DNA (77%) and serious renal disease (53%). The second group (23 patients) had antibodies to Ro and La, and this was associated with a lower incidence of antibodies to DNA (30%) and a very low incidence of nephritis (9%). In this group a phenomenon of linkage of anti- Ro and anti-La titers was observed. Additionally two patients with only anti-La were found. Neither had clinically apparent renal disease. Thus, systemic lupus erythematosus patients with anti-Ro fall into two subgroups that differ considerably in their prevalence of anti-DNA and serious renal disease.

Characterization of the major Epstein-Barr virus-specific RNA in Burkitt lymphoma-derived cells

Cytoplasmic RNA prepared from five lymphoid cell lines and a Burkitt lymphoma biopsy was radioactively labeled in vitro and hybridized to cloned EcoRI restriction endonuclease fragments of B95-8 Epstein-Barr virus DNA. The results confirmed that the most abundant cytoplasmic RNA species in such cells is specified by a small region of the genome defined by the EcoRI J fragment. Detailed mapping experiments precisely localized these transcripts within the sequence of the rightmost one-third of the EcoRI J fragment. DNA sequencing suggested that this region of the Epstein-Barr virus genome is unable to code for protein. The major early transcripts consisted of two non-polyadenylated RNA species, each about 170 nucleotides in length. They were both transcribed off the same strand of the DNA and showed significant sequence homology with each other. The coding sequences of the two small RNAs contained potential intragenic control regions for RNA polymerase III.

Immortalization of human lymphocytes by Epstein-Barr virus

Epstein-Barr virus (EBV) confers upon normal lymphocytes derived from bone marrow the ability to proliferate indefinitely in a test tube. This process, called immortalization, is crucial to the pathogenesis of EBV infections. Inside the immortalized lymphocyte the EBV genome exists as a complete multicopy circular plasmid which is probably not integrated into the cell chromosome. Most of the viral genetic information is not expressed. However, at least six to eight separate regions of the EBV genome encode viral products which are made in the immortalized cell. The identification of the function of these few genes holds some interesting answers to questions concerning the biochemical mechanisms of control of lymphocyte growth and differentiation.

Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells

Small ribonucleic acid (RNA)-protein complexes precipitated by anti-Ro and anti-La antibodies from lupus patients have been examined with emphasis on their RNA components. In both ribonucleoprotein (RNP) classes, the numbers of different RNA molecules and their sequences vary between mouse and human cells. The complex mixtures of La RNAs include two previously sequenced 4.5S RNAs from mouse cells and 5S ribosomal RNA-like molecules from both mouse and human cells. All Ro and La RNAs possess 5-triphosphates. Some La RNAs have internal modifications typical of transfer RNAs. The Ro RNPs are quite stable and are localized by immunofluorescence in the cell cytoplasm, whereas the majority of the La RNPs turn over rapidly and reside in the nucleus. Despite these differences, reconstitution experiments show that the Ro particles carry the La as well as the Ro determinant. Studies using a nuclear transcription system demonstrate that most of the La RNAs are synthesized by RNA polymerase III. The possibility that the La protein(s) functions in the transcription or maturation of all RNA polymerase III transcripts is discussed.

Striking similarities are exhibited by two small Epstein-Barr virus-encoded ribonucleic acids and the adenovirus-associated ribonucleic acids VAI and VAII

The nucleotide sequence of the region of the Epstein-Barr virus genome that specifies two small ribonucleic acids (RNAs), EBER 1 and EBER 2, has been determined. Both of these RNAs are encoded by the right-hand 1,000 base pairs of the EcoRI J fragment of EBV deoxyribonucleic acid. EBER 1 is 166 (167) nucleotides long and EBER 2 is 172 +/- 1 nucleotides long; the heterogeneity resides at the 3' termini. The EBER genes are separated by 161 base pairs and are transcribed from the same deoxyribonucleic acid strand. In vitro, both EBER genes can be transcribed by RNA polymerase III; sequences homologous to previously identified RNA polymerase III intragenic transcription control regions are present. Striking similarities are therefore apparent both between the EBERs and the two adenovirus-associated RNAs, VAI and VAII, and between the regions of the two viral genomes that specify these small RNAs. We have shown that VAII RNA as well as VAI RNA and the EBERs exist in ribonucleoprotein complexes which are precipitable by anti-La antibodies associated with systemic lupus erythematosus. Finally, we have demonstrated that the binding of protein(s) from uninfected cells confers antigenicity on each of the four virus-encoded small RNAs.