[Structural transformations of ribonucleoproteins, formed in the process of self-assembly of small subparticles of Escherichia coli ribosomes].
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Benzenesulfonates↗
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Alternatively spliced transcripts of the sex-determining gene tra-2 of Drosophila encode functional proteins of different size.
The Drosophila transformer-2 gene (tra-2) is required for female sex determination in somatic cells and for spermatogenesis in male germ cells. We studied the organization of the tra-2 gene and characterized the transcripts in wild type and mutant animals. Two transcripts are detected in males and females; they differ in their abundance and in the presence (minor transcript Tmin) or absence (major transcript Tmaj) of one exon. Two other transcripts are present only in male germ cells. One of these is rare (msTmin) and represents a spliced form of the other, more abundant transcript (msTmaj). The transcript Tmaj encodes a protein of 264 amino acids, whereas transcripts Tmin and msTmaj encode proteins that are truncated at the N-terminus. All three putative proteins contain a stretch of approximately 90 amino acids, the ribonucleoprotein motif (RNP motif), which shows similarity to a variety of different ribonucleoproteins. Transformation studies reveal that a cDNA corresponding to the transcript Tmaj can provide all the functions for female sex determination and male fertility. Surprisingly, a cDNA corresponding to the transcript msTmaj could only supply some female sex-determining function, but was unable to restore fertility in mutant males. Sequence analysis of two temperature-sensitive mutations provides evidence that the RNP motif represents an important functional domain of the tra-2 protein.
Amino Acid Sequence↗
La/SSB ribonucleoprotein levels increased in transformed cells.
Autoantibodies to the La/SSB ribonucleoprotein are commonly found in patients with Sjögren's syndrome. Previous studies have shown that La/SSB accumulates in cells shortly after viral infection. We have extended these studies by investigating levels of the La/SSB antigen in virally and spontaneously transformed cell lines (contact-insensitive and tumourigenic) relative to their non-transformed counterpart cell lines (contact-sensitive and non-tumourigenic). Transformed BALB/3T12-3 and KNRK fibroblasts were visibly brighter by immunofluorescence assay than non-transformed BALB/3T3 and NRK fibroblasts respectively, when reacted with anti-La/SSB specific sera. This was confirmed by flow cytometry, as La/SSB levels were elevated in the transformed counterparts of the same cell lines. An anti-Sm monoclonal antibody and normal human serum reacted with these cell lines failed to show a significant increase by flow cytometry. Finally, a two-fold increase in the La/SSB antigen was demonstrated in cell lysates of these cell lines by a capture ELISA. These data show that La/SSB is elevated in transformed cell lines compared with non-transformed counterpart cell lines and suggest that this increase is not restricted to viral transformation.
Animals↗
A cellular protein phosphorylated by the avian sarcoma virus transforming gene product is associated with ribonucleoprotein particles.
In chick embryo fibroblasts transformed by Rous sarcoma virus (RSV) the tyrosine phosphorylation of a cellular protein of 34,000 daltons mol. wt. (34 kd) is greatly enhanced; this was shown to be catalyzed by the phosphotransferase activity of RSV transforming protein pp60src. We report here that in cytoplasmic extracts of both normal and transformed cells, in the presence of magnesium ions, the majority of the 34-kd protein is associated with large structures and that a fraction of 34 kd appears to be associated with ribonucleoprotein particles (RNPs). In addition, upon u.v. light cross-linking of RNA to protein in normal or transformed cells, an anti-34 kd serum immunoprecipitates RNA fragments of apparent low sequence complexity as detected by T1 fingerprint analysis. Our results indicate that the 34-kd protein may play a role in the cell at the level of RNPs.
Animals↗
Translational products of type-C RNA tumor viruses.
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Animals↗
Isolation and characterization of a virus-specific ribonucleoprotein complex from reticuloendotheliosis virus-transformed chicken bone marrow cells.
Chicken bone marrow cells transformed by reticuloendotheliosis virus (REV) produce in the cytoplasm a ribonucleoprotein (RNP) complex which has a sedimentation value of approximately 80 to 100S and a density of 1.23 g/cm3. This RNP complex is not derived from the mature virion. An endogenous RNA-directed DNA polymerase activity is associated with the RNP complex. The enzyme activity was completely neutralized by anti-REV DNA polymerase antibody but not by anti-avian myeloblastosis virus DNA polymerase antibody. The DNA product from the endogenous RNA-directed DNA polymerase reaction of the RNP complex hybridized to REV RNA but not to avian leukosis virus RNA. The RNA extracted from the RNP hybridized only to REV-specific complementary DNA synthesized from an endogenous DNA polymerase reaction of purified REV. The size of the RNA in the RNP is 30 to 35S, which represents the subunit size of the genomic RNA. No 60S mature genomic RNA was found within the RNP complex. The significance of finding the endogenous DNA polymerase activity in the viral RNP in infected cells and the maturation process of 60S virion RNA of REV are discussed.
Animals↗
Glomerular expression of CTGF, TGF-beta 1 and type IV collagen in diabetic nephropathy.
BACKGROUND: In development of progressive extracellular matrix accumulation, connective tissue growth factor (CTGF) may act as a downstream mediator of transforming growth factor-beta 1 (TGF-beta 1). However, the association and the correlation of these cytokines and extracellular matrix accumulation in human diabetic nephropathy (DN) is not fully understood. METHODS: To explore the possible involvement of TGF-beta 1 and CTGF in extracellular matrix accumulation in DN, high-resolution in situ hybridization with digoxigenin-labeled antisense oligonucleotides to CTGF, TGF-beta 1 and type IV collagen mRNAs were performed in DN and in histologically normal human kidney (NHK). To quantify expression of each mRNA, the fraction of all nuclear cells that were positively stained in the cytoplasm was determined in at least 10 randomly selected cross-sections of nonsclerotic glomeruli. RESULTS: Both in DN and in NHK, CTGF, TGF-beta 1 and type IV collagen mRNAs were mainly expressed by glomerular mesangial, visceral epithelial and parietal epithelial cells. The percentages of positive glomerular resident cells were significantly higher for each mRNA in DN compared with NHK. Especially, the expression of CTGF mRNA was also notably increased in case of DN with only mild histopathologic lesions. The extent of expression of each mRNA was significantly correlated to that of each other mRNA examined. CONCLUSION: Our study indicated that CTGF and TGF-beta may play an important role in glomerular histopathologic change in DN.
Adult↗
Efficient protein trafficking requires trailer hitch, a component of a ribonucleoprotein complex localized to the ER in Drosophila.
Translational control of localized messenger mRNAs (mRNAs) is critical for cell polarity, synaptic plasticity, and embryonic patterning. While progress has been made in identifying localization factors and translational regulators, it is unclear how broad a role they play in regulating basic cellular processes. We have identified Drosophila trailer hitch (tral) as a gene that is required for the proper secretion of the dorsal-ventral patterning factor Gurken, as well as the vitellogenin receptor Yolkless. Surprisingly, biochemical purification of Tral revealed that it is part of a large RNA-protein complex that includes the translation/localization factors Me31B and Cup as well as the mRNAs for endoplasmic reticulum (ER) exit site components. This complex is localized to subdomains of the ER that border ER exit sites. Furthermore, tral is required for normal ER exit site formation. These findings raise exciting new possibilities for how the mRNA localization machinery could interface with the classical secretory pathway to promote efficient protein trafficking in the cell.
Animals↗
A streamlined protocol for small-scale protoplast generation and CRISPR/Cpf1-mediated genome editing in Fusarium oxysporum.
Fusarium oxysporum is a significant threat to agriculture and One Health, requiring advanced molecular tools for functional genomic analyses and biological control agent development. Existing gene-editing methods are hampered by costly protoplast preparation protocols and by CRISPR-Cas9 limitations, such as restricted protospacer adjacent motif (PAM) sequences and complex guide RNA requirements. We engineered an efficient CRISPR/Cpf1 system that overcomes these issues through three main innovations: small-scale protoplast generation using filter column-based methods that greatly reduce enzyme consumption while simplifying workflows, a CRISPR/Cpf1 system with shorter guide RNA design and staggered DNA cleavage to promote homologous recombination, and minimal homology arm strategies that significantly decrease cloning complexity. Extensive validation confirms successful gene targeting with molecular verification and functional analysis via standardized pathogenicity assays. This integrated platform offers affordable, accessible tools for systematic F. oxysporum research, enhancing fundamental understanding of plant-pathogen interactions and supporting high-throughput screening vital for agricultural biotechnology and biological agent development.
CRISPR/Cpf1↗
A Xenopus protein related to hnRNP I has a role in cytoplasmic RNA localization.
Cytoplasmic localization of mRNA molecules is a powerful mechanism for generating cell polarity. In vertebrates, one paradigm is localization of Vg1 RNA within the Xenopus oocyte, a process directed by recognition of a localization element within the Vg1 3' UTR. We show that specific base changes within the localization element abolish both localization in vivo and binding in vitro by a single protein, VgRBP60. VgRBP60 is homologous to a human hnRNP protein, hnRNP I, and combined immunolocalization and in situ hybridization demonstrate striking colocalization of hnRNP I and Vg1 RNA within the vegetal cytoplasm of the Xenopus oocyte. These results implicate a novel role in cytoplasmic RNA transport for this family of nuclear RNA-binding proteins.
3' Untranslated Regions↗
The phosphatidylserine receptor: a crucial molecular switch?
The uptake and removal of necrotic or lysed cells involves inflammation and an immune response, due in part to processes that involve members of the collectin family, surface calreticulin and CD91. Clearance of apoptotic cells, by contrast, does not induce either inflammation or immunity. Could the phosphatidylserine receptor be the molecular switch that determines what the outcome will be?
Animals↗
Altered levels of the Drosophila HRB87F/hrp36 hnRNP protein have limited effects on alternative splicing in vivo.
The Drosophila melanogaster genes Hrb87F and Hrb98DE encode the fly proteins HRB87F and HRB98DE (also known as hrp36 and hrp38, respectively) that are most similar in sequence and function to mammalian A/B-type hnRNP proteins. Using overexpression and deletion mutants of Hrb87F, we have tested the hypothesis that the ratio of A/B hnRNP proteins to SR family proteins modulates certain types of alternative splice-site selection. In flies in which HRB87F/hrp36 had been overexpressed 10- to 15-fold above normal levels, aberrant internal exon skipping was induced in at least one endogenous transcript, the dopa decarboxylase (Ddc) pre-mRNA, which previously had been shown to be similarly affected by excess HRB98DE/hrp38. In a second endogenous pre-mRNA, excess HRB87F/hrp36 had no effect on alternative 3' splice-site selection, as expected from mammalian hnRNP studies. Immunolocalization of the excess hnRNP protein showed that it localized correctly to the nucleus, specifically to sites on or near chromosomes, and that the peak of exon-skipping activity in Ddc RNA correlated with the peak of chromosomally associated hnRNP protein. The chromosomal association and level of the SR family of proteins were not significantly affected by the large increase in hnRNP proteins during this time period. Although these results are consistent with a possible role for hnRNP proteins in alternative splicing, the more interesting finding was the failure to detect significant adverse effects on flies with a greatly distorted ratio of hnRNPs to SR proteins. Electron microscopic visualization of the general population of active genes in flies overexpressing hnRNP proteins also indicated that the great majority of genes seemed normal in terms of cotranscriptional RNA processing events, although there were a few abnormalities consistent with rare exon-skipping events. Furthermore, in a Hrb87F null mutant, which is viable, the normal pattern of Ddc alternative splicing was observed, indicating that HRB87F/hrp36 is not required for Ddc splicing regulation. Thus, although splice-site selection can be affected in at least a few genes by gross overexpression of this hnRNP protein, the combined evidence suggests that if it plays a general role in alternative splicing in vivo, the role can be provided by other proteins with redundant functions, and the role is independent of its concentration relative to SR proteins.
Alternative Splicing↗
The Xenopus ELAV protein ElrB represses Vg1 mRNA translation during oogenesis.
Xenopus laevis Vg1 mRNA undergoes both localization and translational control during oogenesis. We previously characterized a 250-nucleotide AU-rich element, the Vg1 translation element (VTE), in the 3'-untranslated region (UTR) of this mRNA that is responsible for the translational repression. UV-cross-linking and immunoprecipitation experiments, described here, revealed that the known AU-rich element binding proteins, ElrA and ElrB, and TIA-1 and TIAR interact with the VTE. The levels of these proteins during oogenesis are most consistent with a possible role for ElrB in the translational control of Vg1 mRNA, and ElrB, in contrast to TIA-1 and TIAR, is present in large RNP complexes. Immunodepletion of TIA-1 and TIAR from Xenopus translation extract confirmed that these proteins are not involved in the translational repression. Mutagenesis of a potential ElrB binding site destroyed the ability of the VTE to bind ElrB and also abolished translational repression. Moreover, multiple copies of the consensus motif both bind ElrB and support translational control. Therefore, there is a direct correlation between ElrB binding and translational repression by the Vg1 3'-UTR. In agreement with the reporter data, injection of a monoclonal antibody against ElrB into Xenopus oocytes resulted in the production of Vg1 protein, arguing for a role for the ELAV proteins in the translational repression of Vg1 mRNA during early oogenesis.
3' Untranslated Regions↗
An immunoprecipitation-RNA:rPCR method for the in vivo isolation of ribonucleoprotein complexes.
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Cell Extracts↗
Transdifferentiation of cardiac fibroblasts, a fetal factor in anti-SSA/Ro-SSB/La antibody-mediated congenital heart block.
The signature lesion of autoantibody-associated congenital heart block (CHB) is fibrosis of the conducting tissue. To date, participation of myofibroblasts in the cascade to injury has been unexplored. The importance of myofibroblast/macrophage cross-talk is demonstrated by the novel finding of these cell types in the heart of a neonate dying of CHB. This clue to pathogenesis prompted consideration of the mechanism by which maternal anti-SSA/Ro-SSB/La Abs initiate an inflammatory response and promote fibrosis. Isolated cardiocytes from 16-24 wk abortuses were rendered apoptotic by exposure to poly (2-) hydroxyethylmethacrylate; flow cytometry confirmed surface expression of Ro/La. Apoptotic cardiocytes were incubated with affinity-purified Abs to 52 and 60 kDa Ro from CHB mothers (opsonized) or IgG fractions from healthy donors (nonopsonized). Macrophages cultured with opsonized apoptotic cardiocytes expressed proinflammatory markers, supported by a three-fold increase in active alpha(V)beta(3) integrin. Fetal cardiac fibroblasts exposed to supernatants obtained from macrophages incubated with opsonized apoptotic cardiocytes (but not nonopsonized) dramatically increased expression of the myofibroblast marker alpha-smooth muscle actin (SMAc). The "opsonized" supernatant reversed an inhibitory effect of the "nonopsonized" supernatant on proliferation of fibroblasts (120 vs 69%, p < 0.05). Parallel experiments examined the effects of two cytokines and their neutralizing Abs on fibroblasts. TGFbeta1 increased SMAc staining but decreased proliferation. TNF-alpha did not affect either readout. Addition of anti-TGFbeta1 Abs to the "opsonized" supernatant blocked SMAc expression but increased proliferation, while anti-TNF-alpha blocking Abs had no effects. These data suggest that transdifferentiation of cardiac fibroblasts to a scarring phenotype is a pathologic process initiated by maternal Abs.
Antibodies, Antinuclear↗
[The release and absorption of small ribonucleoprotein complexes (alpha RNPs) in cultures of transformed rat fibroblasts and human epidermoid carcinoma].
The release of alpha RNPs and their absorbtion by the cells from culture medium were studied. The rat fibroblasts of parental serum-dependent cell line LRec-1, and of selected serum-free cell line LRec-1sf rapidly released and absorbed alpha RNPs. In the latter case, both auto- and heterologous alpha RNPs were seen to penetrate, whereas only autologous alpha RNPs entered LRec-1 cells. Besides, the ability to rapid export and absorbtion of autocrine alpha RNPs was demonstrated for human epidermoid carcinoma cell line A431. Both LRec-1 and LRec-1sf cells expressed mRNAs with homology to ID-like nucleotide sequences, the level of mRNA expression decreasing markedly when serum-dependent LRec-1 cells were grown in serum-free medium.
Animals↗
Expression of folate receptors and heterogeneous nuclear ribonucleoprotein E1 in women with human papillomavirus mediated transformation of cervical tissue to cancer.
AIMS: Folate receptors (FRs) mediate cellular uptake of folates in many cancer cells and in folate deficiency heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) mediates translational upregulation of FR in cultured cervical cancer cells. hnRNP-E1 can also interfere with human papillomavirus 16 (HPV-16) viral capsid protein synthesis (and thereby HPV proliferation) in vitro. This study aimed to evaluate prospectively the relevance of FR and hnRNP-E1 expression in the normal cervix, cervical dysplasia, and cancer. METHODS: Cervical tissues from 12 women with normal histology and 69 consecutive women with varying grades of cervical dysplasia and cancer were prospectively evaluated for immunohistochemical expression of FR, hnRNP-E1, proliferating cell nuclear antigen (PCNA), and HPV. There were 22 women with low grade squamous intraepithelial lesions (LGSIL), 22 with high grade squamous intraepithelial lesions (HGSIL), and 25 with invasive cervical carcinoma. RESULTS: Among normal subjects, 100% and 92% expressed hnRNP-E1 and FR, respectively. FR expression decreased from 91% in LGSIL to 68% and 64% in women with HGSIL and cancer, respectively. Similarly, hnRNP-E1 expression decreased from 86% in LGSIL to 68% and 40% in HGSIL and cancer, respectively. There was a highly significant positive correlation between the extent of FR and hnRNP-E1 expression, and an inverse correlation between HPV infection and hnRNP-E1 expression during progression of cervical dysplasia to cancer. CONCLUSION: These results are consistent with a hypothesis that reduced hnRNP-E1 expression may be permissive for HPV proliferation and progression to cervical cancer, and support the need for prospective longitudinal studies of hnRNP-E1 expression in HPV-16 infected women.
Biomarkers, Tumor↗
Assembly of avian reticuloendotheliosis virus: association of the core precursor polypeptide with the intracellular ribonucleoprotein complex.
A virus-specific ribonucleoprotein complex is present in the cytoplasm of reticuloendotheliosis virus-transformed chicken bone marrow cells. This ribonucleoprotein complex contains viral reverse transcriptase activity and may represent a precursor to the budding virion. The major viral polypeptide associated with the ribonucleoprotein complex was a polypeptide with a molecular weight of 63,000. This protein exhibited a precursor-product relationship with the major reticuloendotheliosis virus structural core protein p29. Core polypeptides were not associated with the intracellular ribonucleoprotein complex. Thus, p29 was incorporated into the virion in the form of its precursor Pr63. The cleavage of Pr63 in the ribonucleoprotein complex was accomplished either during the budding process of shortly after the release of particles from the cell.
Animals↗