Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

With the improved rapid sequencing techniques, the earlier sequence of U2 RNA of Novikoff hepatoma (Shibata et al, J. Biol. Chem. 250, 3909-3920, 1975) was reanalyzed and modified. The improved sequence of U2 RNA is 188 (or 189) nucleotides long and is in register with a characterized U2 RNA pseudogene (Denison et al, PNAS 78, 810-814, 1981) except for an 11 nucleotide sequence (nucleotides 147-157) which is absent from the pseudogene. From these results, a secondary structure of U2 RNA is proposed which is supported by the preferred cleavage sites with T1-RNase, RNase A and S1 nuclease. Isolated U2 RNA was cleaved by T1-RNase preferentially at positions 64 and 164, whereas U2 RNA in U2-snRNP was cleaved only at position 64, indicating that position 164 is protected in U2-snRNP. As with U1 RNA (Epstein et al, PNAS 78, 1562-1566, 1981) the 5'-end of isolated U2 RNA was not preferentially cleaved by T1-RNase.
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PMID:Primary and secondary structure of U2 snRNA. 679 40

Physical, chemical and biological parameters of HeLa cell cultures, which ensure obtaining standard nuclear material to be used as a source of snRNP and snRNA, have been determined. The secondary structure of U1 snRNA as the result of the conformational studies performed using S1 nuclease, A and T1 ribonuclease and Pb(II) ions, and reproducibility of the results obtained after 6-48 h exposure of the cells to actinomycin D at high concentration permit to accept the proposed method of standardization as satisfactory for investigation into snRNP and snRNA.
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PMID:Standardization of HeLa cells preparations as the source of snRNA's for preliminary study on the effectors of pre-mRNA splicing. 750 38

The U1 small nuclear ribonucleoprotein (sn-RNP) particle, which consists of the U1 small RNA and multiple polypeptides, is a central target of the autoimmune response in systemic lupus erythematosus. Autoantibodies to the individual proteins of the U1 snRNP typically co-occur in patients with systemic lupus erythematosus, an observation reconciled by postulating that the intact RNA-protein complex serves as the autoimmunogen and that snRNP-specific autoreactive T cells are necessary for autoantibody production. In this study, we demonstrated that normal mice did not develop antibody responses following immunization with purified self (murine) snRNPs. However, when such mice were coimmunized with self snRNPs in conjunction with the human (foreign) U1 snRNP A protein, they developed autoantibodies directed against individual proteins of the U1 snRNP, in addition to anti-A antibodies; we have previously shown that such mice develop snRNP-specific, autoreactive T cells. Intact snRNPs as a co-immunogen were a prerequisite for antibody expansion, since this response was abrogated by disruption of snRNP particles with pancreatic RNase prior to immunization. These findings indicate that autoreactive helper T cells can drive autoantibody production to the individual proteins of snRNP particles and that such autoantibody responses may require the presence of intact snRNP particles that possess intrastructural B-cell and helper-T-cell determinants. These results also suggest that induction of an immune response to one component of an autoantigenic snRNP complex, possibly through priming with molecular mimics, can induce the diversification of autoantibodies that is characteristic of that found in patients with systemic lupus erythematosus.
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PMID:Role of intermolecular/intrastructural B- and T-cell determinants in the diversification of autoantibodies to ribonucleoprotein particles. 826 62

Small nuclear (sn) ribonucleoprotein (RNP) U2 functions in the splicing of mRNA by recognizing the branch site of the unspliced pre-mRNA. When HeLa nuclear splicing extracts are centrifuged on glycerol gradients, U2 snRNPs sediment at either 12S (under high salt concentration conditions) or 17S (under low salt concentration conditions). We isolated the 17S U2 snRNPs from splicing extracts under nondenaturing conditions by using centrifugation and immunoaffinity chromatography and examined their structure by electron microscope. In addition to common proteins B', B, D1, D2, D3, E, F, and G and U2-specific proteins A' and B", which are present in the 12S U2 snRNP, at least nine previously unidentified proteins with apparent molecular masses of 35, 53, 60, 66, 92, 110, 120, 150, and 160 kDa bound to the 17S U2 snRNP. The latter proteins dissociate from the U2 snRNP at salt concentrations above 200 mM, yielding the 12S U2 snRNP particle. Under the electron microscope, the 17S U2 snRNPs exhibited a bipartite appearance, with two main globular domains connected by a short filamentous structure that is sensitive to RNase. These findings suggest that the additional globular domain, which is absent from 12S U2 snRNPs, contains some of the 17S U2-specific proteins. The 5' end of the RNA in the U2 snRNP is more exposed for reaction with RNase H and with chemical probes when the U2 snRNP is in the 17S form than when it is in the 12S form. Removal of the 5' end of this RNA reduces the snRNP's Svedberg value from 17S to 12S. Along with the peculiar morphology of the 17S snRNP, these data indicate that most of the 17S U2-specific proteins are bound to the 5' half of the U2 snRNA.
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PMID:Small nuclear ribonucleoprotein (RNP) U2 contains numerous additional proteins and has a bipartite RNP structure under splicing conditions. 838 Feb 23

Protein 4.1, originally identified as a component of the membrane-skeleton of the red blood cell, has also been localized in the nucleus of mammalian cells. To learn more about nuclear 4.1 protein, we have analyzed the nature of its association with the nuclear structure in comparison with SC35 and snRNP antigens, splicing proteins of the nuclear speckle domains. When MDCK or HeLa cells were digested with DNase I and washed in the presence of high salt (2 M NaCl), snRNP antigens were extracted whereas protein 4.1 and SC35 remained colocalizing in nuclear speckles. In cells treated with RNase A or heat shocked, nuclear 4.1 distribution also resembled that of SC35. Experiments carried out in transcriptionally active nuclei showed that protein 4.1 distributed in irregularly shaped speckles which appeared to be interconnected. During transcriptional inhibition, protein 4.1 accumulated in rounded speckles lacking interconnections. When cells were released from transcriptional inhibition, protein 4.1 redistributed back to the interconnected speckle pattern of transcriptionally active cells, as it was also observed for SC35. Finally, coprecipitation of 4.1 and SC35 proteins from RNase A digested HeLa nuclei further indicates that these two proteins are associated, forming part of the nuclear speckle domains to which they attach more tightly than snRNP antigens.
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PMID:Transcription-dependent redistribution of nuclear protein 4.1 to SC35-enriched nuclear domains. 904 54

During apoptosis, the U1-70K protein, a component of the spliceosomal U1 snRNP complex, is specifically cleaved by the enzyme caspase-3, converting it into a C-terminally truncated 40-kDa fragment. In this study, we show that the 40-kDa U1-70K fragment is still associated with the complete U1 snRNP complex, and that no obvious modifications occur with the U1 snRNP associated proteins U1A, U1C and Sm-B/B'. Furthermore, it is described for the first time that the U1 snRNA molecule, which is the backbone of the U1 snRNP complex, is modified during apoptosis by the specific removal of the first 5 - 6 nucleotides including the 2,2, 7-trimethylguanosine (TMG) cap. The observations that U1 snRNA cleavage is very specific (no such modifications were detected for the other U snRNAs tested) and that U1 snRNA cleavage is markedly inhibited in the presence of caspase inhibitors, indicate that an apoptotically activated ribonuclease is responsible for the specific modification of U1 snRNA during apoptosis.
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PMID:The fate of U1 snRNP during anti-Fas induced apoptosis: specific cleavage of the U1 snRNA molecule. 1071 22

Splicing and polyadenylation factors interact for the control of polyadenylation and the coupling of splicing and polyadenylation. We document an interaction between the U1 snRNP and mammalian polyadenylation cleavage factor I (CF Im), one of several polyadenylation factors needed for the cleavage of the pre-mRNA at the polyadenylation site. Sucrose density gradient centrifugation demonstrated that CF Im separated into two fractions, a light fraction which contained the known CF Im subunits (72, 68, 59, and 25 kD), and a heavy fraction, rich in snRNPs, which contained predominately the 68- and 25-kD CF Im subunits. Using specific antibodies we found that the heavy fraction contains U1 snRNP/CF Im coprecipitable complexes. These complexes were insensitive to RNase treatment, suggesting that the coprecipitation is not due to RNA tethering. In vitro binding experiments show that both the 68- and 25-kD subunits bind to and comigrate with U1 snRNP. In addition, the 25-kD CF Im subunit binds specifically to the 70K protein of U1 snRNP (U1 70K). This binding may account for the CF Im/U1 snRNP interaction. During these studies we found that mAb 2.73 (mAb 2.73), an established U1 70K antibody, efficiently precipitates the bulk of the CF Im from cellular extracts. Because mAb 2.73 has been used in a number of previous studies related to the U1 snRNP and the U1 70K protein, the precipitation of CF Im must be considered in evaluating past and future data based on the use of mAb 2.73.
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PMID:Association of polyadenylation cleavage factor I with U1 snRNP. 1456 89

The poly(A)-limiting element (PLE) restricts the length of the poly(A) tail to <20 nt when present in the terminal exon of a pre-mRNA. We previously identified a 65 kDa protein that could be cross-linked to a functional PLE, but not to an inactive mutant element. This binding was competed by poly(U) and poly(C), but not poly(A) or poly(G). Selectivity for the pyrimidine-rich portion of the PLE was demonstrated by RNase footprinting of the binding activity in total nuclear extract. A 65 kDa protein that selectively cross-linked to the functional PLE was purified by conventional chromatography and identified as the large subunit of U2 snRNP auxiliary factor (U2AF). Overexpression of U2AF65 in cells transfected with a PLE-containing reporter construct resulted in the appearance of a population of mRNAs with heterogeneous poly(A) tails. However, this effect was lost following deletion of the C-terminal RNA recognition motifs (RRMs). A C-->G mutation following the AG dinucleotide in the PLE resulted in mRNA with poly(A) ranging from 25-50 nt. This reverted to a discrete, <20 nt poly(A) tail in cells expressing U2AF65. Our results suggest that U2AF modulates the function of the PLE, perhaps by facilitating the binding of another protein to the element.
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PMID:U2AF modulates poly(A) length control by the poly(A)-limiting element. 1457 15

The U1 snRNP-A (U1A) protein has been known for many years as a component of the U1 snRNP. We have previously described a form of U1A present in human cells in significant amounts that is not associated with the U1 snRNP or U1 RNA but instead is part of a novel complex of non-snRNP proteins that we have termed snRNP-free U1A, or SF-A. Antibodies that specifically recognize this complex inhibit in vitro splicing and polyadenylation of pre-mRNA, suggesting that this complex may play an important functional role in these mRNA-processing activities. This finding was underscored by the determination that one of the components of this complex is the polypyrimidine-tract-binding protein-associated splicing factor, PSF. In order to further our studies on this complex and to determine the rest of the components of the SF-A complex, we prepared several stable HeLa cell lines that overexpress a tandem-affinity-purification-tagged version of U1A (TAP-tagged U1A). Nuclear extract was prepared from one of these cell lines, line 107, and affinity purification was performed along with RNase treatment. We have used mass spectrometry analysis to identify the candidate factors that associate with U1A. We have now identified and characterized PSF, p54(nrb), and p68 as novel components of the SF-A complex. We have explored the function of this complex in RNA processing, specifically cleavage and polyadenylation, by performing immunodepletions followed by reconstitution experiments, and have found that p54(nrb) is critical.
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PMID:p54nrb is a component of the snRNP-free U1A (SF-A) complex that promotes pre-mRNA cleavage during polyadenylation. 1637 96

We have raised antibodies against the profilin of Chironomus tentans to study the location of profilin relative to chromatin and to active genes in salivary gland polytene chromosomes. We show that a fraction of profilin is located in the nucleus, where profilin is highly concentrated in the nucleoplasm and at the nuclear periphery. Moreover, profilin is associated with multiple bands in the polytene chromosomes. By staining salivary glands with propidium iodide, we show that profilin does not co-localize with dense chromatin. Profilin associates instead with protein-coding genes that are transcriptionally active, as revealed by co-localization with hnRNP and snRNP proteins. We have performed experiments of transcription inhibition with actinomycin D and we show that the association of profilin with the chromosomes requires ongoing transcription. However, the interaction of profilin with the gene loci does not depend on RNA. Our results are compatible with profilin regulating actin polymerization in the cell nucleus. However, the association of actin with the polytene chromosomes of C. tentans is sensitive to RNase, whereas the association of profilin is not, and we propose therefore that the chromosomal location of profilin is independent of actin.
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PMID:Profilin is associated with transcriptionally active genes. 2257 53


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