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PubMed1998

Skeletal muscle immune deposits in systemic lupus erythematosus. Correlation with histologic changes, autoantibodies, and clinical involvement.

Skeletal muscle biopsy and autopsy samples of 132 SLE patients were studied by immunofluorescence and light microscopic techniques. Immune deposits were compared to histologic abnormalities and clinical and serologic findings. Immune deposits with a mainly granular pattern were observed at different locations in 49 patients (37%). They correlated significantly (p<0.001) with inflammatory myopathy, demonstrated in 33(25%), with noninflammatory myopathy which occurred in 38 (29%) vasculitis, observed in 13(10%), and with noninflammatory vasculopathy which was noted in 10 patients (8%). The correlation of muscle immune deposits with anti-DNA antibodies was significant at p= 0.016. Anti-Sm and anti-U1 RNP antibodies were associated significantly with the intensity of immune deposits. Furthermore, a correlation of immune deposits with increased creatine phosphokinase and myopathic electromyogram, but not with evidence of clinical involvement, was shown. A key pathogenetic role of immune deposits in the development of skeletal muscle histologic abnormalities in SLE was demonstrated.

Adolescent↗

PubMed1995

Identification of the factors that interact with NCBP, an 80 kDa nuclear cap binding protein.

It has been shown that the monomethylated cap structure plays important roles in pre-mRNA splicing and nuclear export of RNA. As a candidate for the factor involved in these nuclear events we have previously purified an 80 kDa nuclear cap binding protein (NCBP) from a HeLa cell nuclear extract and isolated its full-length cDNA. In this report, in order to obtain a clue to the cellular functions of NCBP, we attempted to identify a factor(s) that interacts with NCBP. Using the yeast two-hybrid system we isolated three clones from a HeLa cell cDNA library. We designated the proteins encoded by these clones NIPs (NCBP interacting proteins). NIP1 and NIP2 have an RNP consensus-type RNA binding domain, whereas NIP3 contains a unique domain of Arg-Glu or Lys-Glu dipeptide repeats. We also show that NCBP requires NIP1 for binding to the cap structure. Possible roles of NIPs in cap-dependent nuclear processes are discussed.

Amino Acid Sequence↗

PubMed1985

The Raji cell radioimmunoassay in patients with systemic lupus erythematosus: clinical significance and relationship to other serologic variables assessed by discriminant analysis.

Our aim was to determine the clinical usefulness of the Raji cell radioimmunoassay (RIA) in 30 patients with systemic lupus erythematosus (SLE) studied over a 30-month period. Raji RIA correlated positively (p less than 0.001) with antibodies to dsDNA, anti-Sm, erythrocyte sedimentation rate and central nervous system involvement and inversely with the white blood count, hematocrit and CH50. There was a lack of correlation (p greater than 0.05) between the Raji RIA and cryoglobulins, Clq binding assay, lymphocyte count, rheumatoid factor and anti-RNP. Raji RIA values paralleled disease activity in 50% and were predictive of flares in 17%. By discriminant analysis, the Raji RIA could not predict nephritis as well as a variety of routine laboratory tests in SLE. The Raji RIA, while helpful in SLE, does not appear to offer any advantage over standard assays in monitoring SLE disease activity.

Antigen-Antibody Complex↗

PubMed1979

Nucleolar reorganization in liver cells of the aging rat.

The nucleoli of rat liver cells duplicate in great detail the life-long series of reorganizational changes encountered in kidney and intestinal epithelial cells. The ultrastructural components of the large, loosely organized polymorphous nucleoli, which are dominant in the rapidly multiplying stem cells of embryos, are readily accessible for chemical activities. Smaller, more compact amphinucleoli are dominant in more mature cells, which were characterized by Smetana ('70) as "idling" cells, showing slowly continuing ribosome formation and RNP synthesis. In older cells bipartite nucleoli become dominant and are reorganized in increasing numbers from the younger amphinucleoli. These, however, are not replaced in equal numbers from the shrinking pool of polymorphs of young cells which have greatly reduced mitotic potential. Paralleling the shifts in dominant nucleolar types, the high level of protein synthesis declines in older cells not only in the quantity of proteins synthesized but also in kinds of enzymes produced. These fail to meet the structural and functional requirements of aging cells leading ultimately to the onset of age-related degenerative changes. Again it is noted that separation of the karyosomal DNA from the plasmosomal RNA-protein complex of the nucleolus may lead to possible breakdown of the DNA-dependent RNA-protein transcription system ultimately bringing protein synthesis to a very low level in the senescent animal.

Aging↗

PubMed1981

Antibodies to Sm in patients with systemic lupus erythematosus. Correlation of Sm antibody titers with disease activity and other laboratory parameters.

Thirty patients with systemic lupus erythematosus (SLE) were studied over a 2.5-year period. The group was divided into 14 patients with antibodies to Sm and a control group that failed to exhibit antibodies to Sm over the study period. The titer of antibodies to Sm fluctuated in all 14. A rising titer of antibodies to Sm 1) predicted a flare disease in 50% an 2) correlated with an exacerbation of disease in 60%. Patients with antibodies to Sm had a comparable incidence of severe disease, renal disease, and central nervous system disease. They exhibited significantly more leukopenia and antibodies to non-Sm, non-RNP extractable nuclear antigen. In only 1 patient, a rise in titer of antibodies to Sm did not correlate with or predict a disease flare in contradistinction to other serologic markers of SLE, specifically antibodies to double-stranded DNA and cryoglobulins. Though infrequently detected, antibodies to Sm can help in the management of patients with SLE.

Adolescent↗

PubMed2000

Intestinal pseudo-obstruction in systemic lupus erythematosus: an uncommon but important clinical manifestation.

OBJECTIVES: To document intestinal pseudo-obstruction (IpsO) as a recognised clinical manifestation of systemic lupus erythematosus (SLE) and a possible new clinical entity with its apparent association with ureterohydronephrosis. METHODOLOGY: We report six lupus patients who presented with IpsO and review 12 other cases from an English literature search. IpsO is defined as the presence of clinical features suggestive of intestinal obstruction but without organic obstruction, namely absence of bowel sounds, presence of multiple fluid levels on plain abdominal X-rays and exclusion of organic obstruction by imaging or surgical procedure. Other clinical characteristics related to the underlying lupus, serological and histological findings, treatment modalities and outcomes of these patients were reviewed. RESULTS: All 18 patients fulfilled the ACR revised classification criteria for SLE. None showed any clinical features of scleroderma or overlap syndrome. The mean age of onset of IpsO was 29.0 (15-47) y. The female to male ratio was 16:2. Nine patients had IpsO as the initial presentation of their underlying lupus. Coexisting lupus involvement of other organ systems included glomerulonephritis (n=7), thrombocytopenia (n=5) and cerebral lupus (n=3). The serology data and autoantibody profile of some of the previously reported patients were incomplete. In our series, anti-Ro antibody was positive in 5/6 while anti-RNP was found in 1/6 patients only. All our patients had active lupus serology at presentation. 17/18 patients required the use of high dose systemic corticosteroid therapy while one patient responded to topical adrenocorticotrophin hormone treatment. Response was good and was observed early after commencement. Azathioprine was used as maintenance therapy in 6/18 patients with good effects. An apparent association with the presence of bilateral ureterohydronephrosis was found in 12/18 patients. These patients presented with dysuria without positive bacterial culture though features of chronic interstitial cystitis were not invariably found in these patients. CONCLUSION: IpsO is an uncommon but important manifestation of SLE. The underlying pathology is not fully understood but it may be related to immune complex deposition. The finding of coexisting ureterohydronephrosis suggests that there may also be a central smooth muscle motility problem of neuropathic or myogenic pathophysiology which may or may not be secondary to vasculitis. Early recognition and treatment of IpsO in SLE is important.

Adult↗

PubMed2000

[Nucleoli and perinuclear bodies in trophocytes of Panorpa communis contain factors of pre-mRNA splicing].

The distribution of pre-mRNA splicing factors and protein coilin was examined in trophocyte nuclei (TN) in polytrophic ovarioles of Panorpa communis. In situ hybridization, using antisense U1 and U6 snRNA 3H-riboprobes, showed that TN were labeled evenly. Immunostaining at light and electron microscopic levels revealed in some TN nucleolar structures containing small nuclear RNP (snRNP) and protein coilin characteristic of the Cajal bodies/coiled bodies (CB). No free CBs were found in TN. These data showed that CB in TN are present only in the nucleoli. One of characteristic features of P. communis trophocytes is the presence of several types of perinuclear bodies (PB) in the cytoplasm. We distinguish between three types of PBs. PB-1 consist of spherical bodies (10-20 microns) with vacuoles composed of closely packed fibrils. PB-2 are irregularly shaped bodies (0.3-2.0 microns) consisting of a fibro-granular material. PB-2 are located near the nuclear envelope and contact the nucleoplasm material through nuclear pores. PB-1 and PB-2 join together to form a complex PB of the third type. All types of PB are not surrounded with a membrane and sometimes have mitochondria on their surface. The immunogold technique at the ultrastructural level revealed snRNP in PB-2. These results have enabled us to make a conclusion that PB-2 may be storage sites of snRNPs required for a future development of the embryo.

Animals↗

PubMed2004

[Selective effect of inductors of apoptosis on the endoribonuclease activity of 26S proteasomes and alpha-RNP particles in K562 cells: possible involvement of 26S proteasomes and alpha-RNP in the regulation of RNA stability].

It has been shown that endoribonuclease activity of alpha-RNP particles and 26S proteasomes are changed under the action of inductors of programmed cell death. Treatment of K562 cells with inductors of apoptosis--doxorubicin (adriamycin) and diethylmaleate--lead to a significant stimulation of RNAse activity of alpha-RNP and to reduction of proteasome RNase activity. The enzymatic activity under study has been shown to be specifically and selectively dependent on phosphorylation of subunits of alpha-RNP particles and 26S proteasomes. The characteristics of RNAse activity of different subpopulations of proteasomes differ. The specificity of a subpopulation of proteasomes exported from the cell has been demonstrated. Proteasome and alpha-RNP involvement in the coordinated control of stability of various specific messenger RNA molecules is suggested, and one of the mechanisms of this control might be the export of specific subpopulation of proteasomes from the cell.

Apoptosis↗

PubMed1986

RNA-protein organization of U1, U5 and U4-U6 small nuclear ribonucleoproteins in HeLa cells.

Small nuclear ribonucleoproteins (snRNPs) containing U1 and U5 snRNAs from HeLa cells have been fractionated using a combination of isopycnic centrifugation in cesium chloride and ion-exchange chromatography on DEAE-Sepharose. The procedure is based on the extreme stability conferred upon snRNPs by Mg2+ enabling them to withstand the very high ionic strength that prevails in cesium chloride. U1 snRNP prepared by this method contains all nine major proteins (68K, A, B, B', C, D, E, F, G) corresponding to those previously identified by immunoprecipitation and is therefore precipitable by anti-RNP and anti-Sm antibodies. U5 snRNP purified in this way contains the common D to G proteins and is also enriched in a 25 X 10(3) Mr protein that may be U5 snRNP-specific. The core-resistant U5 snRNA sequence (nucleotide 84 to 3' OH) covered by D to G proteins is extended by only six nucleotides. A similar situation is seen in U4-U6 snRNP, which we have obtained in a sufficiently pure form to examine protected sequences. However, the core-resistant sequence of U4 (nucleotide 116 to 3' OH) in U4-U6 snRNP is extended by 37 nucleotides, suggesting that the protein composition of this particle could be more complex than that of U5 snRNP. The ribonucleoprotein organization of snRNPs is summarized and discussed in view of our current knowledge on snRNA sequences protected by proteins.

Base Sequence↗

PubMed1998

Identification of human autoantigen La/SS-B as BC1/BC200 RNA-binding protein.

Rodent BC1 RNA and primate BC200 RNA are small cytoplasmic non-messenger RNAs that are phylogenetically unrelated. Nevertheless, the two RNAs exhibit a large degree of parallelism. In addition to some sequence similarities in their 3' domains, they are prevalently expressed in a similar subset of neurons and belong to a small group of transcripts with a somatodendritic location. Both RNAs are complexed with proteins as ribonucleoprotein particles (RNPs). Their similarities may even extend to analogous functional roles, for example, in the regulation of decentralized dendritic translation. To shed further light on the physiological role(s) of the BC1/BC200 RNPs, we began to analyze protein components that specifically bind to these RNAs. Ultraviolet-crosslinking experiments and affinity purification techniques revealed that the human autoantigen La/SS-B is associated with BC1/BC200 RNA in vitro and in vivo. As with other RNA polymerase III transcripts, La protein binds with high affinity to the 3' end of BC200 RNA. Our results suggest that an additional function of La may be control of dendritic translation by providing a link between the 5' Alu domain of BC200 RNP and the ribosome via the La protein dimer. The fact that La binds both BC1 and BC200 RNAs further supports the notion that the RNAs are functional analogs despite the fact that they arose from two separate retroposition events in two different mammalian lineages.

Animals↗

PubMed1985

Analysis of cytoplasmic 19 S ring-type particles in Drosophila which contain hsp 23 at normal growth temperature.

Cytoplasmic 19 S particles were isolated from postpolysomal supernatants of 25 degrees C Drosophila embryos and culture cells. The particles were purified by salt extraction and sucrose gradient centrifugation. Electron microscopic investigation showed that the 19 S particles possess a ring-shaped morphology with an outer diameter of 12 nm and a hollow core of 3 nm. Biochemically the particles are characterized by a group of 16 polypeptides within the molecular weight range of 35 to 23 kDa, and small RNA molecules in the size range of 200 to 60 nucleotides. The RNP character of the particles is also shown by their buoyant density in Cs2SO4 of rho = 1.29 g/cm3 and their susceptibility to uv crosslinking and density in CsCl of rho = 1.38 g/cm3. Antibodies were raised against the proteins of the 19 S particles isolated from 25 degrees C cells and tested by immunoblotting after one- and two-dimensional gel-electrophoresis. Two of the antibodies raised cross react with the small heat-shock proteins hsp 28/27 and hsp 23. Comparative protease V8 cleavage of hsp 23 and the 23-kDa particle protein demonstrates that these two proteins are identical and that the small hsp of Drosophila must be a genuine part of the 19 S cytoplasmic ring-shaped complexes at normal growth temperature. The data support the idea of a general developmental role of some of the so-called heat-shock proteins.

Animals↗

PubMed1992

Definition of a discontinuous immunodominant epitope at the NH2 terminus of the La/SS-B ribonucleoprotein autoantigen.

High-titer IgG autoantibodies to the La/SS-B ribonucleoprotein (RNP) are a hallmark of patients with primary Sjogren's syndrome. Anti-La/SS-B-positive human sera bind to multiple epitopes on recombinant La/SS-B, although the initial response is against an immunodominant epitope within the first 107 NH2-terminal amino acids (aa). Sequence analysis has identified a striking homology between aa 88-101 in this NH2-terminal region of La/SS-B and a feline retroviral gag polypeptide suggesting the anti-La/SS-B response may be initiated by cross-reactivity with an exogenous agent. In the present study, detailed mapping of this NH2-terminal epitope, using recombinant La/SS-B purified from the expression of overlapping DNA fragments spanning aa 1-107, has shown that this immunodominant epitope is a complex conformational or discontinuous epitope dependent upon both aa 12-28 and 82-99 for expression, even though these regions share no homology with each other. This requirement questions the significance of the homology between La/SS-B and a retroviral gag polypeptide in the generation of the B cell response to La/SS-B and is in accord with the general concept that B cells recognize conformational epitopes on antigens rather than small linear peptide sequences. The finding also reinforces the notion that native autoantigen could be the initiator of the autoimmune response.

Autoantibodies↗

PubMed1982

The reaction of human SLE antibodies with native, single stranded RNA: analysis of nucleotide sequence specificities and correlation with Sm and nRNP activities.

The antigenic specificities of RNA reactive IgG autoantibodies from three individual human SLE sera and pooled NZB/NZW mouse serum were studied by competition reactions with synthetic co-polymers and heteropolymers of varying nucleotide compositions. Although minor differences in the individual binding patterns were noted, the RNA reactive immunoglobulins showed a clear preference for G, C and G,C,U containing RNA sequences. All three SLE sera had Sm or RNP activities with rabbit thymus extractable nuclear antigen (ENA). Conversely, all SLE sera that were selected on the basis of their positive ENA reaction could also bind free, single stranded RNA. These results suggest that the autoimmune response to RNA in human and murine SLE is restricted to one or a very few antigenic determinants. They also raise the possibility that autoantibodies to native RNA in SLE sera are partly responsible for ENA reactivity.

Antigen-Antibody Complex↗

PubMed2002

Biogenesis of yeast telomerase depends on the importin mtr10.

Telomerase is a ribonucleoprotein particle (RNP) involved in chromosome end replication, but its biogenesis is poorly understood. The RNA component of yeast telomerase (Tlc1) is synthesized as a polyadenylated precursor and then processed to a mature poly(A)- form. We report here that the karyopherin Mtr10p is required for the normal accumulation of mature Tlc1 and its proper localization to the nucleus. Neither TLC1 transcription nor the stability of poly(A)- Tlc1 is significantly affected in mtr10delta cells. Tlc1 was mostly nuclear in a wild-type background, and this localization was not affected by mutations in other telomerase components. Strikingly, in the absence of Mtr10p, Tlc1 was found dispersed throughout the entire cell. Our results are compatible with two alternative models. First, Mtr10p may import a cytoplasmic complex containing Tlc1 and perhaps other components of telomerase, and shuttling of Tlc1 from the nucleus to the cytoplasm and back may be necessary for the biogenesis of telomerase (the "shuttling" model). Second, Mtr10p may be necessary for the nuclear import of some enzyme needed for the nuclear processing and maturation of Tlc1, and in the absence of this maturation, poly(A)+ Tlc1 is aberrantly exported to the cytoplasm (the "processing enzyme" model).

Cell Compartmentation↗

PubMed1991

Analysis of protein--RNA interactions within Ro ribonucleoprotein complexes.

The interactions between Ro and La proteins and hY RNAs have been analysed. The binding site for the 60 kDa Ro protein on hY RNAs is shown to be the terminal part of the base paired stem structure, which contains the most highly conserved sequence among hY RNAs. The bulged C-residue within this region plays an important role in the recognition by this protein. The same regions of hY RNAs are essential for the association of the 52 kDa Ro protein with the RNAs, strongly suggesting that the 60 kDa Ro protein is required for the 52 kDa Ro protein to bind, presumably via protein-protein interactions, to Ro RNPs. The binding site for the La protein on hY RNAs is shown to be the oligouridylate stretch near the 3'-end of the RNAs, which is also recognized when additional nucleotides flank this motif at the 3'-side. Additional sequence elements in hY3 and hY5, but not in hY1, are bound by the La protein as well. Deletion mutagenesis showed that the RNP motif, previously identified in many ribonucleoprotein (RNP) proteins and in some cases shown to be almost sufficient for the interaction with RNA, of both the 60 kDa Ro and the La protein are not sufficient for the interaction with hY RNAs. Substantial parts of these proteins flanking the RNP motif are needed as well. It is likely that they stabilize the correct conformation of the RNP motif for RNA binding.

Base Composition↗

PubMed2005

Molecular basis for RNA kink-turn recognition by the h15.5K small RNP protein.

The interaction between box C/D small nucleolar (sno)RNAs and the 15.5K protein nucleates snoRNP assembly. Many eukaryotic snoRNAs contain two potential binding sites for this protein, only one of which appears to be utilized in vivo. The binding site conforms to the consensus for a kink-turn motif. We have investigated the molecular basis for selection of one potential site over the other using in vitro mobility shift assays and nucleotide analog interference mapping of Xenopus U25 snoRNA and of a circularly permuted form. We find that preferential binding of human 15.5K is not dependent on the proximity of RNA ends, but instead appears to require a structural context beyond the kink-turn itself. Direct analysis of the energetic contributions to binding made by 18 functional groups within the kink-turn identified both backbone atoms and base functionalities as key for interaction. An intramolecular RNA-RNA contact via a 2'-hydroxyl may supercede a putative Type I A-minor interaction in stabilizing the RNA-protein complex.

Animals↗

PubMed1997

Transportin-mediated nuclear import of heterogeneous nuclear RNP proteins.

Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 is an abundant nuclear protein that plays an important role in pre-mRNA processing and mRNA export from the nucleus. A1 shuttles rapidly between the nucleus and the cytoplasm, and a 38-amino acid domain, M9, serves as the bidirectional transport signal of A1. Recently, a 90-kD protein, transportin, was identified as the mediator of A1 nuclear import. In this study, we show that transportin mediates the nuclear import of additional hnRNP proteins, including hnRNP F. We have also isolated and sequenced a novel transportin homolog, transportin2, which may differ from transportin1 in its substrate specificity. Immunostaining shows that transportin1 is localized both in the cytoplasm and the nucleoplasm, and nuclear rim staining is also observed. The nuclear localization of A1 is dependent on ongoing RNA polymerase II transcription. Interestingly, a pyruvate kinase-M9 fusion, which normally localizes in the nucleus, also accumulates in the cytoplasm when RNA polymerase II is inhibited. Thus, M9 itself is a specific sensor for transcription-dependent nuclear transport. Transportin1-A1 complexes can be isolated from the cytoplasm and the nucleoplasm, but transportin1 is not detectable in hnRNP complexes. RanGTP causes dissociation of A1-transportin1 complexes in vitro. Thus, it is likely that after nuclear import, A1 dissociates from transportin1 by RanGTP and becomes incorporated into hnRNP complexes, where A1 functions in pre-mRNA processing.

Animals↗

PubMed2007

Altered protamine expression and diminished spermatogenesis: what is the link?

During the elongating spermatid stage of spermiogenesis, human sperm chromatin undergoes a complex transition in which histones are extensively replaced by protamines in a carefully regulated transition including histone modifications and intermediate and temporary replacement of the histones by sperm-specific transition proteins. The replacement of most histones by protamines 1 and 2 facilitates a high order of chromatin packaging necessary for normal sperm function and may also be necessary for DNA silencing and imprinting changes within the sperm cell. Protamines 1 and 2 are usually expressed in nearly equal quantities, but elevated or diminished protamine 1/protamine 2 ratios are observed in some infertile men and is often associated with severe spermatogenesis defects. Human and animal studies demonstrate that expression of the protamine proteins is uniquely regulated by transcription/translation factors, including storage of the mRNA in ribonucleoprotein (RNP) particles composed of the mRNA, transcription factors and a kinesin molecule necessary for transport of the RNP to the cytoplasm and removal of transcriptional activators from the nucleus. Recent studies indicate that most patients with abnormal protamine protein levels have elevated levels of protamine transcript in the mature sperm cell, indicating a possible defect in transcription or translation. The regulation of protamine expression is unique and includes several possible mechanisms which may be responsible for dysregulation of protamine expression and concurrent broad spectrum defects in spermatogenesis. We suggest two hypotheses: (i) that abnormal protamine expression is indicative of a generalized defect in mRNA storage and/or translation which affects other mRNA transcripts or (ii) that protamines may act as a checkpoint of spermatogenesis.

Animals↗