The primary structure of the acidic phosphoprotein P2 from rat liver 60 S ribosomal subunits. Comparison with ribosomal 'A' proteins from other species

A review and meta-analysis of anti-ribosomal P autoantibodies in systemic lupus erythematosus

The discovery of autoantibodies to ribosomal proteins (anti-RibP) dates back more than fifty years when antibodies to ribosomes were identified in systemic lupus erythematosus (SLE) sera. Over the years, anti-RibP autoantibodies have been the subject of extensive study and became known as a highly specific biomarker for the diagnosis of SLE and were associated with neuropsychiatric SLE (NPSLE), lupus nephritis (LN) and hepatitis (LH). As demonstrated by studies on cultured human cells and of murine models, there is evidence to suggest that anti-RibP may have a pathogenic role in LN and NPSLE. Despite a wealth of evidence, in comparison to other SLE autoantibodies such as anti-Sm and anti-dsDNA, anti-RibP has not been included in classification criteria for SLE. A significant challenge is the variability of assays used to detect anti-RibP, including the antigens and diagnostic platforms employed. This may account for the marked variation in frequencies (10-47%) in SLE and its association with clinical and demographic features reported in SLE cohorts. We performed a systematic literature review and meta-analysis to help clarify its prevalence, various clinical and serological associations in SLE based on the different RibP antigens and assay platforms used.

Organelles do not colocalize with mRNA granules in post-ischemic neurons

Following global brain ischemia and reperfusion, it is well-established that neurons undergo a translation arrest that is reversible in surviving neurons, but irreversible in vulnerable neurons. We previously showed a correlation between translation arrest in reperfused neurons and the presence of granular mRNA-containing structures we termed "mRNA granules." Here we further characterized the mRNA granules in reperfused neurons by performing colocalization studies using fluorescent in situ hybridization for poly(A) mRNAs and immunofluorescence histochemistry for markers of organelles and mRNA-binding proteins. There was no colocalization between the mRNA granules and markers of endoplasmic reticulum, cis- or trans-Golgi apparatus, mitochondria, microtubules, intermediate filaments, 60S ribosomal subunits, or the HuR ligands APRIL and pp32. The mRNA granules colocalized with the neuronal marker NeuN regardless of the relative vulnerability of the neuron type. RNA immunoprecipitation of HuR from the cytoplasmic fraction of 8 h reperfused forebrains selectively isolated hsp70 mRNA suggesting the mRNA granules are soluble structures. Together, these results rule out several organelle systems and a known HuR pathway as being directly involved in mRNA granule function.

Three-dimensional studies of pathogenic peptides from the c-terminal of Trypanosoma cruzi ribosomal P proteins and their interaction with a monoclonal antibody structural model

The acidic C-terminal peptides from Trypanosoma cruzi ribosomal P proteins are the major target of the antibody response in patients suffering Chagas chronic heart disease. It has been proposed that the disease is triggered by the cross-reaction of these antibodies with the second extra cellular loop of the beta1-adrenoreceptor, brought about by the molecular mimicry between the acidic C-terminal peptides and the receptor's loop. To improve the understanding of the structural basis of the autoimmune response against heart receptors, the 3-dimensional structure of the C-terminal peptides of Trypanosoma cruzi ribosomal proteins P0 (EDDDDDFGMGALF) and P2beta (EEEDDDMGFGLFD) were solved using the Electrostaticaly Driven MonteCarlo method. Their structures were compared with the second extra-cellular loop of our homology model of human rhodopsin and the existing experimental NMR structures of the C-terminal peptides from human P0 (EESDDDMGFGLFD) and from Leishmania braziliensis P0 (EEADDDMGFGLFD). Docking of Trypanosoma cruzi peptides P0, P2beta and human rhodopsin loop into our anti-P2beta monoclonal antibody homology model allowed to explore their interactions.The solution structure of peptides P0 and P2beta can be briefly described as a bend. Although the global conformations of the peptides are not identical they shared a common region of four residues (3 to 6) that have a similar structure. The structural alignment of the five peptides also showed a surprising conformational similarity for the same residues. The antibody model and docking studies revealed a most remarkable feature in the active site, a positively charged, narrow and deep cavity where the acidic residues 3 to 6 were accommodated. These results suggest that the most important elements in the molecular peptide recognition by the antibody may be the shape of the loop and the presence of negative charges in positions 3-5 (P0, P2beta) or a negative charge in position 4 (rhodopsin loop). This work describes clearly the interactions of the structural elements involved in the autoimmune mechanism of anti-P auto-antibodies cross-reaction and stimulation of the beta1-adrenoreceptor and the visual pigment rhodopsin. Results from this study could lead eventually to the development of treatments to abolish receptor mediated symptoms in Chagas. PACS code: 87.15.-v.

Genes coding structural proteins in the Leishmania braziliensis complex

Acidic ribosomal P1 and P2b proteins, referred to as P proteins, and histone H3 are reported for first time in the Leishmania braziliensis complex. Deoxyribonucleic acid analysis and multiple sequence alignment suggest that both P proteins may maintain their structural function in the ribosomal stalk, in spite of the high rate of mutations detected. The deduced amino acid sequence of protein P1 showed 51% identity with Trypanosoma cruzi protein P1 and protein P2b showed 61% identity with T. cruzi protein P2b. Another conserved protein, L. (Viannia) braziliensis histone H3, showed 82% and 70% identity with histone H3 of L. (Leishmania) infantum and T. cruzi, respectively. The N-terminal end of this histone is divergent in comparison with the consensus eukaryotic sequence. Their predicted tridimensional structure was designed.

Asymmetric interactions between the acidic P1 and P2 proteins in the Saccharomyces cerevisiae ribosomal stalk

The Saccharomyces cerevisiae ribosomal stalk is made of five components, the 32-kDa P0 and four 12-kDa acidic proteins, P1alpha, P1beta, P2alpha, and P2beta. The P0 carboxyl-terminal domain is involved in the interaction with the acidic proteins and resembles their structure. Protein chimeras were constructed in which the last 112 amino acids of P0 were replaced by the sequence of each acidic protein, yielding four fusion proteins, P0-1alpha, P0-1beta, P0-2alpha, and P0-2beta. The chimeras were expressed in P0 conditional null mutant strains in which wild-type P0 is not present. In S. cerevisiae D4567, which is totally deprived of acidic proteins, the four fusion proteins can replace the wild-type P0 with little effect on cell growth. In other genetic backgrounds, the chimeras either reduce or increase cell growth because of their effect on the ribosomal stalk composition. An analysis of the stalk proteins showed that each P0 chimera is able to strongly interact with only one acidic protein. The following associations were found: P0-1alpha.P2beta, P0-1beta.P2alpha, P0-2alpha.P1beta, and P0-2beta.P1alpha. These results indicate that the four acidic proteins do not form dimers in the yeast ribosomal stalk but interact with each other forming two specific associations, P1alpha.P2beta and P1beta.P2alpha, which have different structural and functional roles.

Yeast protein phosphatase active with acidic ribosomal proteins

A protein phosphatase dephosphorylating acidic ribosomal proteins was purified from Saccharomyces cerevisiae ribosome-free extract. It was shown that phosphoproteins from both P1 and P2 subfamilies as well as 60S "core" P0 protein were substrates for the enzyme. The phosphatase can dephosphorylate ribosomes as well as histones and casein but the two last substrates with significantly lower efficiency. It was found that the enzyme activity is Mn(2+)-dependent and inhibited by okadaic acid, tautomycin, cantharidin and nodularin at concentrations typical for protein phosphatase type 2A. The possible implications of those findings in the control of ribosome phosphorylation and therefore in the control of translation is discussed.

Structure and function of the stalk, a putative regulatory element of the yeast ribosome. Role of stalk protein phosphorylation

The ribosomal stalk is involved directly in the interaction of the elongation factors with the ribosome during protein synthesis. The stalk is formed by a complex of five proteins, four small acidic polypeptides and a larger protein which directly interacts with the rRNA at the GTPase center. In eukaryotes, the acidic components correspond to the 12 kDa P1 and P2 proteins, and the RNA binding component is protein P0. All these proteins are found to be phosphorylated in eukaryotic organisms. Previous in vitro data suggested this modification was involved in the activity of this structure. To confirm this possibility a mutational study has shown that phosphorylation takes place at a serine residue close to the carboxyl end of proteins P1, P2 and P0. This serine is part of a consensus casein kinase II phosphorylation site. However, by using a yeast strain carrying a temperature sensitive mutant, it has been shown that CKII is probably not the only enzyme responsible for this modification. Three new protein kinases, RAPI, RAPII and RAPIII, have been purified and compared with CKII and PK60, a previously reported enzyme that phosphorylates the stalk proteins. Differences among the five enzymes have been studied. It has also been found that some typical effectors of the PKC kinase stimulate the in vitro phosphorylation of the stalk proteins. All the data available suggest that phosphorylation, although it is not involved in the interaction of the acidic proteins with the ribosome, affects ribosome activity and might participate in some ribosome regulatory mechanism.

Phosphorylation of the yeast ribosomal stalk. Functional effects and enzymes involved in the process

The ribosomal stalk is directly involved in the interaction of the elongation factors with the ribosome during protein synthesis. The stalk is formed by a complex of five proteins, four small acidic polypeptides and a larger protein which directly interacts with the rRNA at the GTPase center. In eukaryotes the acidic components correspond to the 12-kDa P1 and P2 proteins, and the RNA binding component is the P0 protein. All these proteins are found phosphorylated in eukaryotic organisms, and previous in vitro data suggested this modification was involved in the activity of this structure. Results from mutational studies have shown that phosphorylation takes place at a serine residue close to the carboxy end of the P proteins. Modification of this serine residue does not affect the formation of the stalk and the activity of the ribosome in standard conditions but induces an osmoregulation-related phenotype at 37 degrees C. The phosphorylatable serine is part of a consensus casein kinase II phosphorylation site. However, although CKII seems to be responsible for part of the stalk phosphorylation in vivo, it is probably not the only enzyme in the cell able to perform this modification. Five protein kinases, RAPI, RAPII and RAPIII, in addition to the previously reported CKII and PK60 kinases, are able to phosphorylate the stalk proteins. A comparison of the five enzymes shows differences among them that suggest some specificity regarding the phosphorylation of the four yeast acidic proteins. It has been found that some typical effectors of the PKC kinase stimulate the in vitro phosphorylation of the stalk proteins. All the data suggest that although phosphorylation is not involved in the interaction of the acidic P proteins with the ribosome, it can affect the ribosome activity and might participate in a possible ribosome regulatory mechanism.

Structure-function relationships in the ribosomal protein L12 in the archaeon Sulfolobus acidocaldarius

A series of mutant L12 ribosomal proteins was prepared by site-directed mutations in the L12 protein gene of the archaeon Sulfolobus acidocaldarius. The mutant protein genes were overexpressed in Escherichia coli, and the products purified and incorporated into ribosomal cores which had been ethanol extracted to remove wild-type L12 protein. Measurements were made to determine if the mutation affected the binding of the L12 protein to the ribosome core or affected the translational activity of the resulting ribosome. Changing tyrosine [3] or tyrosine [5], conserved in all archaea and present in all eukarya in positions [3] and [7], to phenylalanine had no effect on binding or translational activity while changes to glycine significantly reduced binding and translational activity. Changing the single arginine [37] residue, conserved in almost all archaeal and eukaryal L12 proteins, to lysine, glutamic acid, glutamine, or glycine had no effect on binding to the core and had little or no significant effect on translational activity. The same was true when lysine [39], conserved in all archaeal L12 proteins, was changed to arginine, glutamic acid, glutamine, or glycine. Changing phenylalanine [104], the penultimate amino acid at the C-terminal end, which is conserved in all archaeal and eukaryal L12 proteins, to tyrosine or glycine had no effect on binding but lowered the translational activity by 60 and 75%, respectively, suggesting that this amino acid plays an important role in translation. Deletion of the highly charged region in the C-terminal domain, which is present in all archaeal and eukaryal L12 proteins, decreased transitional activity by 50%, suggesting this region is also involved in factor interactions.

RAP kinase, a new enzyme phosphorylating the acidic P proteins from Saccharomyces cerevisiae

A new protein kinase, showing a high specificity for the ribosomal acidic P proteins (RAP kinase) has been purified and characterized from Saccharomyces cerevisiae extracts. Purification was carried out by four chromatographic steps, including DEAE-cellulose, phosphocellulose, heparin-Sepharose and P protein-Sepharose. The purified enzyme preparation contains only one polypeptide of around 55 kDa as determined by SDS gel electrophoresis and gradient centrifugation. RAP kinase is different from all previous well-characterized kinases and does not show cross-reaction with antibodies to the 71 kDa 60S ribosomal subunit-specific kinase PK60 previously reported. The enzyme uses ATP as a better phosphate donor and is less sensitive to heparin than casein kinase II but is moderately affected by salt. Among the different substrates tested, ribosomal acidic proteins are preferentially modified by RAP kinase, which phosphorylates only serine residues in the four P proteins as well as the related ribosomal protein P0. Casein is phosphorylated at a much lower level. All the data indicate that RAP kinase might be the enzyme responsible for the phosphorylation of the P proteins, and in this way may also participate in a possible translational regulatory mechanism.

Characterization of a maize ribosomal P2 protein cDNA and phylogenetic analysis of the P1/P2 family of ribosomal proteins

The nucleotide sequence of a full-length ribosomal P2 protein cDNA from maize was determined and used for a sequence comparison with the P2 and P1 proteins from other organisms. The integration of these data into a phylogenetic tree shows that the P proteins separated into the subspecies P1 and P2 before the eukaryotic kingdoms including plants developed from their ancestor.

Structure and evolution of mammalian ribosomal proteins

Mammalian (rat) ribosomes have 80 proteins; the sequence of amino acids in 75 have been determined. What has been learned of the structure of the rat ribosomal proteins is reviewed with particular attention to their evolution and to amino acid sequence motifs. The latter include: clusters of basic or acidic residues; sequence repeats or shared sequences; zinc finger domains; bZIP elements; and nuclear localization signals. The occurrence and the possible significance of phosphorylated residues and of ubiquitin extensions is noted. The characteristics of the mRNAs that encode the proteins are summarized. The relationship of the rat ribosomal proteins to the proteins in ribosomes from humans, yeast, archaebacteria, and Escherichia coli is collated.

Eukaryotic acidic phosphoproteins interact with the ribosome through their amino-terminal domain

Variable-size fragments of the four yeast acidic ribosomal protein genes rpYP1 alpha, rpYP1 beta, rpYP2 alpha and rpYP2 beta were fused to the LacZ gene in the vector series YEp356-358. The constructs were used to transform wild-type Saccharomyces cerevisiae and several gene-disrupted strains lacking different acidic ribosomal protein genes. The distribution of the chimeric proteins between the cytoplasm and the ribosomes, tested as beta-galactosidase activity, was estimated. Hybrid proteins containing around a minimum of 65-75 amino acids from their amino-terminal domain are able to bind to the ribosomes in the presence of the complete native proteins. Hybrid proteins containing no more than 36 amino terminal amino acids bind to the ribosomes in the absence of a competing native protein. The fused YP1-beta-galactosidase proteins are also able to form a complex with the native YP2 type proteins, promoting their binding to the ribosome. The stability of the hybrid polypeptides seems to be inversely proportional to the size of their P protein fragment. These results indicate that only the amino-terminal domain of the eukaryotic P proteins is needed for the P1-P2 complex formation required for interaction with the ribosome. The highly conserved P protein carboxyl end is not implicated in the binding to the particles and is exposed to the medium.

Antiribosomal antibodies in SLE, infection, and following deliberate immunization

ARA occur in approximately 10% of randomly selected SLE patients but in up to 40% of patients with active disease. Anti-P antibodies appear to be a highly specific diagnostic marker for SLE since they are rarely detected in other multisystem autoimmune disorders. ARA are most frequently directed against the P proteins and the shared conserved C-terminus of the P proteins is immunodominant in almost all sera tested. Anti-P antibodies increase in titer in patients with active disease and have been reported to be detected more frequently in patients with severe behavioral disturbances. This may be particularly true of patients with affective disorders. The clinical utility of serological tests for anti-P in central nervous system lupus must await large, prospective studies. Other ARA antibodies have been detected in patients with SLE. These antibodies include anti-28S rRNA, anti-S10, and anti-L12. In all cases, the frequency with which these antibodies are detected is increased in sera containing anti-P. The P proteins and the 28S rRNA epitope play essential, but as yet undefined, roles in GTPase activity on the ribosome. The L12 protein is the mammalian homologue of the E. coli and yeast proteins known to bind to the 28S rRNA epitope. These findings indicate that some SLE patients produce autoantibodies against multiple components of a functionally related domain of the ribosome. This, in turn, supports the notion that the ribosome initiates and/or maintains autoantibody production. Despite the evidence supporting an antigen driven immune response, attempts to induce anti-P antibodies by immunization with autologous ribosomes in the autoimmune strain of mouse, MRL, have been unsuccessful. It therefore seems likely that the ribosomal components must be altered in some way to break tolerance or that other abnormalities of the immune system are necessary for autoantibody production. Immunization with foreign ribosomes induce anti-P autoantibodies in mice and in apparently normal humans infected with the hemoflaggelate, T. cruzi. The ability of the P proteins to break tolerance in these situations is, most likely, explained by the provision of a T cell epitope (the foreign P protein) together with the multivalency of the P proteins on the ribosome (which activate autoreactive B cells). We therefore propose (Fig. 5) a two-signal model for autoantibody production similar to that suggested for T-B collaboration in the normal immune response and also in the GVHD model of lupus.(ABSTRACT TRUNCATED AT 400 WORDS)

Drosophila acidic ribosomal protein rpA2: sequence and characterization

A cDNA encoding the Drosophila melanogaster acidic ribosomal protein rpA2 was cloned and sequenced. rpA2 is homologous to the Artemia salina acidic ribosomal protein eL12'. In situ hybridization to salivary gland polytene chromosomes localizes the rpA2 gene to band 21C. It is a single copy gene, with an mRNA of 0.8 kb. Two-dimensional gel electrophoresis of Drosophila ribosomal proteins followed by immuno-blotting showed that the rpA2 protein has an apparent relative mobility in SDS of 17 kD and an isoelectric point less than pH 5.0. Although the Drosophila gene rp21C may be the same as rpA2, the reported sequences differ. Comparisons of the aligned nucleotide sequences coding for the acidic ribosomal proteins rpA1 and rpA2 of Drosophila with those of other eukaryotes support the view of two separate, though closely related, groups of acidic proteins. Comparison with the Artemia homologues suggests that nucleotide identity may have been conserved by some constraint that acts in addition to the requirement for substantial similarity of amino acid sequences.

Ribosomal protein P2, a novel iron-binding protein

We examined the properties of a new iron-binding protein purified previously from rat liver (T. Furukawa, S. Taketani, H. Kohno, and R. Tokunaga, 1991, Biochem. Biophys. Res. Commun. 181, 409-415). The protein was digested with trypsin and the peptides were analyzed by reverse-phase high-performance liquid chromatography. The partial amino acid sequences of the tryptic peptides coincided with that of rat ribosomal protein P2. Immunoblot analysis and iron-binding assay confirmed that the iron-binding protein and ribosomal protein P2 are identical. Then the iron binding ability of ribosomal protein P2 was examined in rat hepatoma H4IIEC3 cells incubated with radioactive iron. When immunoprecipitation with anti-iron-binding protein serum was performed using cells incubated with 59Fe-citrate, about 4% of the 59Fe radioactivity in cells was associated with the iron-binding protein through 30 to 90 min of incubation. About 1.5% of radioactive iron in cells incubated with 59Fe-transferrin was found in immunoprecipitates with anti-iron-binding protein serum during 1 to 5 h of incubation, and 4 to 7% of the radioactivity was found in immunoprecipitates with a monoclonal antibody against ribosomal P proteins in the same incubation. These results demonstrate that ribosomal proteins P2 binds iron taken up by the cells.

Molecular action of tricholin, a ribosome-inactivating protein isolated from Trichoderma viride

An extracellular protein was isolated from a species of soil-borne fungi (Trichoderma viride) and its amino acid composition has been determined. The protein is acidic with a molecular mass of 14,200 daltons and is given the trivial name tricholin. Tricholin is a potent inhibitor of cell-free protein synthesis. When rabbit reticulocyte lysate was incubated with tricholin at a concentration of 6.3 x 10(-7) M, it completely abolished the capacity of the lysate to support protein synthesis. The inhibition appears to be due to its reaction to ribosomes, since it generates a specific cleavage product, an alpha-sarcin RNA fragment, from reticulocyte ribosomal RNA. This reaction to ribosomes mimics that of alpha-sarcin. The antibody of alpha-sarcin strongly cross-reacts with tricholin, while the antibody of tricholin shows a weak reaction with alpha-sarcin.

Localization of surface peptide from ribosomal protein L7 on 80 S ribosome by biotinylation

A surface topography of ribosomal peptides on ribosome particles was conducted by using N',Hydroxysuccinimido-biotin (NHS-biotin) modification. All rat ribosomal proteins, except proteins L3 and L8, are biotinylated when the ribosome particle is the substrate. A surface peptide from protein L7 was determined from biotinylated ribosomes by high performance liquid chromatography and cyanogen bromide peptide mapping. It was found that only the tandem repeats of the NH2-terminal segment of protein L7 are accessible to biotinylation. It is concluded that the NH2-terminal-end of protein L7 should be exposed on the surface of ribosomal particles.

The primary structure of rat ribosomal proteins P0, P1, and P2 and a proposal for a uniform nomenclature for mammalian and yeast ribosomal proteins

The covalent structures of rat ribosomal proteins P0, P1, and P2 were deduced from the sequences of nucleotides in recombinant cDNAs. P0 contains 316 amino acids and has a molecular weight of 34,178; P1 has 114 residues and a molecular weight of 11,490: and P2 has 115 amino acids and a molecular weight of 11,684. The rat P-proteins have a near identical (16 of 17 residues) sequence of amino acids at their carboxyl termini and are related to analogous proteins in other eukaryotic species. A proposal is made for a uniform nomenclature for rat and yeast ribosomal proteins.

The binding site of ribosomal protein L10 in eubacteria and archaebacteria is conserved: reconstitution of chimeric 50S subunits

It has been shown by electron microscopy that the selective removal of the stalk from 50S ribosomal subunits of two representative archaebacteria, namely Methanococcus vaniellii and Sulfolobus solfataricus, is accompanied by loss of the archaebacterial L10 and L12 proteins. The stalk was reformed if archaebacterial core particles were reconstituted with their corresponding split proteins. Next, structurally intact chimeric 50S subunits have been reconstituted in vitro by addition of Escherichia coli ribosomal proteins L10 and L7/L12 to 50S core particles from M vaniellii or S solfataricus, respectively. In the reverse experiment, using core particles from E coli and split proteins from M vaniellii, stalk-bearing 50S particles were also obtained. Analysis of the reconstituted 50S subunits by immunoblotting revealed that E coli L10 was incorporated into archaebacterial core particles in both presence or absence of E coli L7/L12. In contrast, incorporation of E coli L7/L12 into archaebacterial cores was only possible in the presence of E coli L10. Our results suggest that in archaebacteria - as in E coli - the stalk is formed by archaebacterial L12 proteins that bind to the ribosome via L10. The structural equivalence of eubacterial and archaebacterial L10 and L12 proteins has thus for the first time been established. The chimeric reconstitution experiments provide evidence that the domain of protein L10 that interacts with the ribosomal particle is highly conserved between eubacteria and archaebacteria.

Characterization of the yeast acidic ribosomal phosphoproteins using monoclonal antibodies. Proteins L44/L45 and L44' have different functional roles

In order to characterize the acidic ribosomal proteins immunologically and functionally, a battery of monoclonal antibodies specific for L44, L44' and L45, the three acidic proteins detected in Saccharomyces cerevisiae, were obtained. Eight monoclonal antibodies were obtained specific for L45, three for L44' and one for L44. In addition, two mAbs recognizing only the phosphorylated forms of the three proteins were obtained. The specific immunogenic determinants are located in the middle region of the protein structure and are differently exposed in the ribosomal surface. The common determinants are present in the carboxyl end of the three proteins. An estimation of the acidic proteins by ELISA indicated that, in contrast to L44 and L45, L44' is practically absent from the cell supernatant; this suggests that protein L44' does not intervene in the exchange that has been shown to take place between the acidic proteins in the ribosome and in the cytoplasmic pool. It has also been found that, while IgGs specific for L44 and L45 do not inhibit the ribosome activity, the anti-L44' effectively blocks the polymerizing activity of the particles. These results show for the first time that the different eukaryotic acidic ribosomal proteins play a different functional role.

Major Trypanosoma cruzi antigenic determinant in Chagas' heart disease shares homology with the systemic lupus erythematosus ribosomal P protein epitope

A Trypanosoma cruzi lambda gt11 cDNA clone, JL5, expressed a recombinant protein which was found to react predominantly with chronic Chagas' heart disease sera. The cloned 35-residue-long peptide was identified as the carboxyl-terminal portion of a T. cruzi ribosomal P protein. The JL5 13 carboxyl-terminal residues shared a high degree of homology with the systemic lupus erythematosus (SLE) ribosomal P protein epitope. Synthetic peptides comprising the 13 (R-13), 10 (R-10), and 7 (R-7) carboxyl-terminal residues of the JL5 protein were used to study, by enzyme-linked immunosorbent assay, the specificity of the Chagas' disease anti-JL5 and SLE anti-P antibodies. The R-13 peptide defined a linear antigenic determinant of the JL5 recombinant protein. As was proved for JL5, R-13 defined antibody specificities which were significantly increased in chronic Chagas' heart disease patients. Only SLE anti-P positive sera were found to react with JL5 and R-13. Fine epitope mapping showed that Chagas' disease anti-JL5 and SLE anti-P antibodies define similar epitopes within the R-13 peptide. The binding of the SLE sera to JL5 was completely blocked by the R-13 peptide, indicating that the shared specificity between anti-JL5 and anti-P autoantibodies was exclusively limited to the conserved linear epitope(s) within the R-13 peptide. The prevalence of high anti-R-13 antibody titers in Chagas' heart disease patients supports the hypothesis that postulates the existence of autoimmune disorders in Chagas' heart disease.

Glucocorticoids repress ribosome biosynthesis in lymphosarcoma cells by affecting gene expression at the level of transcription, posttranscription and translation

Growth arrest of P1798 murine lymphosarcoma cells by glucocorticoids is accompanied by a remarkable decrease in transcription of rRNA and translation of mRNAs encoding basic ribosomal proteins (rps). Here we report that the expression of other genes involved in ribosome biogenesis is repressed in dexamethasone-treated P1798 cells. These include posttranscriptionally regulated decline in the abundance of the mRNA and primary transcript of nucleolin; abrupt drop in the transcription rate of U3 small nucleolar RNA; and inhibition of translation of mRNAs coding for P2 and L5, acidic and basic rps, respectively. Normal expression of these genes is resumed upon hormonal withdrawal.

A family of genes encode the multiple forms of the Saccharomyces cerevisiae ribosomal proteins equivalent to the Escherichia coli L12 protein and a single form of the L10-equivalent ribosomal protein

The budding yeast Saccharomyces cerevisiae contains a family of genes that encodes four different but related small acidic ribosomal proteins designated L12eIA, L12eIB, L12eIIA, and L12eIIB and a single larger protein designated L10e. These proteins are equivalent (e) to the L12 and L10 proteins of Escherichia coli that assemble as a 4:1 complex onto the large ribosomal subunit. The five yeast genes (or their cDNAs) have been cloned and sequenced (M. Remacha, M. T. Saenz-Robles, M. D. Vilella, and J. P. G. Ballesta, J. Biol. Chem. 263:9044-9101, 1988; K. Mitsui and K. Tsurugi, Nucleic Acids Res. 16:3573, 3574, and 3575, 1988; this work). Here, the transcripts of these genes were characterized and quantitated and the proteins they encode were compared and aligned. Four of the genes, L12eIA, -IB, -IIA, and L10e, are uninterrupted, whereas the L12eIIB gene contains a 301-nucleotide-long intron between codons 38 and 39. The transcripts derived from each of these genes were analyzed by Northern (RNA) hybridization, primer extension, and S1 nuclease protection. All five genes are expressed, albeit at different levels. The transcript levels are coordinate and exhibit growth rate-dependent regulation in rich (glucose) and poor (ethanol) media. The five yeast proteins each contain a highly conserved acidic carboxy terminus of about 20 residues in length. This domain of unknown function is also present in archaebacterial but absent from eubacterial L10e and L12e proteins. Comparisons of the factor-binding domains in the yeast and other eucaryotic and archaebacterial L12e proteins indicate that the original duplication to produce the type I and II genes was a very ancient event. The evolutionary relationships between the eucaryotic, archaebacterial, and eubacterial L10e and L12e genes (and proteins) are discussed.

Ribosome and protein synthesis modifications after infection of human epidermoid carcinoma cells with herpes simplex virus type 1

Modifications of ribosomes have been investigated in human epidermoid carcinoma-2 cells at different stages of herpes simplex virus type 1 infection. Very early in infection, there is an increase in ribosomal protein S6 phosphorylation even in the absence of serum. The same result is obtained in the presence of actinomycin D. At early infection time, ribosomal proteins S2, S3a and Sa are newly phosphorylated. At early and early-late times, three phosphorylated non-ribosomal proteins (v1, v2 and v3) are differently associated temporally to ribosomes. Analyses of proteins extracted from 40S subunits, 80S ribosomes and polysomes show that v1 and v2 are distributed differently among the different ribosomal populations. S6 phosphopeptides were found to be identical after serum stimulation and after viral infection. In every case phosphoserine and phosphothreonine were identified in S6. Only phosphoserine was found in other phosphorylated proteins. Our results indicate that herpes simplex virus type 1 is able to modify pre-existing ribosomes: (i) by stimulating a pre-existing kinase for S6 phosphorylation even in the absence of serum and of viral genome expression; (ii) by inducing new specific kinase activity(ies); and (iii) by association of new, phosphorylated proteins to ribosomes. These ribosomal modifications are correlated with changes in protein synthesis, as shown by two-dimensional electrophoretic analyses of newly synthesized 35S-labelled proteins.

Sequence alignment and evolutionary comparison of the L10 equivalent and L12 equivalent ribosomal proteins from archaebacteria, eubacteria, and eucaryotes

The genes corresponding to the L10 and L12 equivalent ribosomal proteins (L10e and L12e) of Escherichia coli have been cloned and sequenced from two widely divergent species of archaebacteria, Halobacterium cutirubrum and Sulfolobus solfataricus. The deduced amino acid sequences of the L10e and L12e proteins have been compared to each other and to available eubacterial and eucaryotic sequences. We have identified the human P0 protein as the eucaryotic L10e. The L10e proteins from the three kingdoms were found to be colinear. The eubacterial L10e protein is much shorter than the archaebacterial-eucaryotic proteins because of two large deletions, one internal and one at the carboxy terminus. The archaebacterial and eucaryotic L12e proteins were also colinear; the eubacterial protein is homologous to the archaebacterial and eucaryotic L12e proteins, but has suffered rearrangement through what appear to be gene fusion events. Intraspecies comparisons between L10e and L12e sequences indicate the archaebacterial and eucaryotic L10e proteins contain a partial copy of the L12e protein fused to their carboxy terminus. In the eubacteria most of this fusion has been removed by the carboxy terminal deletion. Within the L12e-derived region, a 26-amino acid-long internal modular sequence reiterated thrice in the archaebacterial L10e, twice in the eucaryotic L10e, and once in the eubacterial L10e was discovered. This modular sequence also appears to be present as a single copy in all L12e proteins and may play a role in L12e dimerization, L10e-L12e complex formation, and the function of L10e-L12e complex in translation.(ABSTRACT TRUNCATED AT 250 WORDS)

The primary structure of rat ribosomal protein L37a

The amino acid sequence of rat ribosomal protein L37a was deduced from the sequence of nucleotides in recombinant cDNAs isolated in Yamagata and in Chicago and confirmed from the NH2-terminal amino acid sequence of the protein. Ribosomal protein L37a contains 91 amino acids (the NH2-terminal methionine is removed after translation of the mRNA) and has a molecular mass of 10143 Da.

The primary structure of rat ribosomal protein S4

The amino acid sequence of the rat 40 S ribosomal subunit protein S4 was deduced from the sequence of nucleotides in a recombinant cDNA and confirmed from the NH2-terminal amino-acid sequence of the protein. Ribosomal protein S4 has 282 amino acids (the NH2-terminal methionine is removed after translation of the mRNA) and has a molecular weight of 31,841. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 7-11 copies of the S4 gene. The mRNA for the protein is about 1 kb in length. Rat S4 is homologous to Saccharomyces cerevisiae YS6. The protein contains a possible internal duplication of 11 residues.

The primary structure of rat ribosomal protein S10

The amino acid sequence of rat ribosomal protein S10 was deduced from the sequence of nucleotides in a recombinant cDNA and confirmed from the NH2-terminal amino acid sequence of the protein. Ribosomal protein S10 contains 165 amino acids and has a molecular mass of 18917 Da. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 17-20 copies of the S10 gene. The mRNA for the protein is about 750 nucleotides in length. Ribosomal protein S10 has several possible internal duplications; one is a tandem repeat of ten residues that is basic and contains two or three prolines.

The complete sequence of a chicken-muscle cDNA encoding the acidic ribosomal protein P1

We have isolated and sequenced a complete cDNA encoding the acidic phosphoprotein P1 from chicken. The analysis of the deduced protein sequence and its comparison with the known sequence of P proteins from human, rat and Artemia salina indicates that the central, alanine-rich region of these proteins was probably generated by internal duplications of the gene followed by modifications within each repeat. This observation explains the length heterogeneity and sequence divergence of this particular region when compared with the highly conserved structure of the remaining segments of the protein.

Nucleotide sequence of cloned cDNA specific for rat ribosomal protein L27

We constructed cDNA libraries from 8-9-S poly(A)-rich RNA from regenerating rat liver, isolated clones specific for ribosomal protein L27 and determined the nucleotide sequences of the cDNA clones. The longest cDNA consists of 15 base pairs from the 5' leading sequence, the entire coding sequence of 411 base pairs, and the 3' trailing sequence of 59 base pairs including the poly(A) tail. The primary structure of protein L27 was deduced from the sequence of nucleotides. Protein L27 contains 135 amino acids and has a molecular mass of 15,666 Da. The amino-terminal sequence agreed well with the published partial amino acid sequence and the calculated amino acid composition is also consistent with the reported composition determined for the hydrolyzate of L27.

The primary structure of rat ribosomal protein L18

The amino acid sequence of rat ribosomal protein L18 was deduced from the sequence of nucleotides in a recombinant cDNA and confirmed from the amino-terminal amino acid sequence of the protein. Ribosomal protein L18 contains 187 amino acids (the amino-terminal methionine is removed after translation of the mRNA) and has a molecular weight of 21,530. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 10-14 copies of the L18 gene. Rat ribosomal protein L18 is homologous to Xenopus laevis L14; the extent of the identity of the amino acid sequences is 87% and for the nucleotides in the coding region of the DNA it is 76%.

5S-rRNA-containing ribonucleoproteins from rabbit muscle and liver. Complex and partial primary structures

A 5S-rRNA-containing ribonucleoprotein was purified to homogeneity from a rabbit muscle extract through its affinity to phosphofructokinase-1 and then structurally characterized. This RNP was compared to the 5S-rRNA-containing ribonucleoprotein extracted from rabbit liver ribosomal 60S subunits with EDTA. Analytical gel filtration revealed a molecular mass of 70-80 kDa for both complexes. Gel electrophoresis of the ribosomal complex revealed three protein components, one migrating as a band of 35 kDa and two other small polypeptides of apparently 16.5 kDa and 17.5 kDa. In the sarcoplasmic RNP these small polypeptides were absent. However, besides a major component of 35 kDa, up to five slightly larger and smaller species of 31.5-36.5 kDa were detected. Despite this heterogeneity, only one N-terminal amino acid sequence was obtained for the isolated sarcoplasmic protein, suggesting a C-terminal heterogeneity of one single polypeptide. Within the first 46 amino acid residues no difference between the sequences of the isolated 35-kDa components of sarcoplasmic and ribosomal complexes was found. Homology criteria indicated that this component belongs to the ribosomal protein L5 family. The RNA was identified by complete enzymatic sequencing as 5S rRNA; it was also identical in both complexes and is strongly homologous to 5S rRNA of man. Both L5-5S-RNA complexes could be resolved by hydroxyapatite chromatography into three species still consisting of both protein and RNA. 5'-Terminal dephosphorylation experiments showed that this heterogeneity is exclusively due to the differing number (1-3) of 5'-terminal phosphates. The two additional low-molecular-mass proteins were stably associated to the ribosomal RNP at high salt concentrations in a stoichiometry of about 2:1. They were identified as the acidic phosphoproteins P2/P3 by N-terminal sequencing. High phosphate concentrations facilitated their dissociation from the L5-5S-RNA complex. For the sarcoplasmic L5-5S-RNA complex a hitherto unknown interaction with phosphofructokinase-1, affecting the enzymatic properties, was demonstrated.