Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Differentiation inhibiting activity/leukemia inhibitory factor (DIA/LIF) is a glycoprotein that controls differentiation of pluripotential stem cells. Alternative transcription generates both diffusible and matrix-associated forms of DIA/LIF. Transcriptional analysis using a sensitive ribonuclease protection assay revealed that the two messages are expressed independently, consistent with the proposition that the two forms of DIA/LIF have distinct biological roles. DIA/LIF expression was found to be activated early during differentiation of embryonic stem (ES) cells, providing a mechanism for feedback regulation of stem cell renewal. Expression of DIA/LIF by mesenchymal cells was shown to be controlled in a paracrine manner by polypeptide regulatory factors. Specific expression of the two forms of DIA/LIF was also demonstrated in the egg cylinder-stage mouse embryo. The combination of cell type-specific and signal-specific regulation enables very precise control over DIA/LIF expression and may represent an important component of the regulatory networks that govern stem cell proliferation and differentiation during mammalian development.
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PMID:Developmentally programmed induction of differentiation inhibiting activity and the control of stem cell populations. 170 81

We have shown that the developmentally regulated appearance of the two myelin-associated glycoprotein (MAG) polypeptides in normal mouse brain myelin does not reflect the developmental pattern of differential splicing of primary gene transcripts as determined earlier by RNase protection assays. Contrary to expectation, the large (L-MAG) and small (S-MAG) polypeptides are present in about equal amounts at a relatively early stage of myelination, day 24 or earlier. In quaking (qk) mutant mouse brain myelin, both MAG polypeptides are evident at all ages examined; the relatively greater abundance of S-MAG compared to L-MAG at early ages (days 18 and 22) confirms our earlier observation on in vitro translations of mRNA. At later ages (day 27 and beyond) both isoform are present in approximately equal amounts. The L-MAG but not the S-MAG polypeptide can be phosphorylated by kinases that are endogenous to isolated qk myelin, analogous to the phosphorylation we have observed in vivo in normal mice and in their isolated myelin.
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PMID:Two isoforms of myelin-associated glycoprotein accumulate in quaking mice: only the large polypeptide is phosphorylated. 170 10

The DNA polymerase and RNase H activities of HIV reverse transcriptase are both essential for HIV replication. Although the two activities are both catalyzed by a single polypeptide, they are physically separate; i.e., the DNA polymerase resides in the N-terminal domain whereas the RNase H is localized in the C-terminal domain. The present study was undertaken to characterize the enzymatic properties of these two activities and to determine whether the two catalytic sites are also functionally distinct. We have observed that EGTA specifically stimulates, whereas CaCl2 selectively inhibits, the RNA-dependent DNA polymerase activity but that neither compound has any effect on the RNase H activity of a recombinant HIV reverse transcriptase. The stimulation of the DNA polymerase activity by EGTA is dependent on the Mg2+ concentration; the greatest stimulation is observed at low Mg2+ concentrations. Similarly, the inhibition of DNA polymerase activity by Ca2+ is influenced by Mg2+ concentration. Ca2+ inhibition can be reversed by increasing Mg2+ concentrations, suggesting the possibility that CaCl2 inhibits the reverse transcriptase activity by competing for a metal-binding site on the enzyme. The pyrophosphate analogue phosphonoformate selectively inhibits the polymerase activity but not the RNase H activity of HIV reverse transcriptase. In contrast, the RNase H activity can be selectively inhibited by deoxyadenosine 5'-monophosphate, whereas the DNA polymerase activity is not inhibited. These results suggest that the DNA polymerase and RNase activities are not only physically separate but that they are also functionally distinct.
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PMID:Functional characterization of RNA-dependent DNA polymerase and RNase H activities of a recombinant HIV reverse transcriptase. 170 16

It is generally assumed that the machinery that transcribes genes is composed entirely of polypeptides. However, in vitro transcription by silkworm RNA polymerase III requires a transcription factor that is not a polypeptide. This component, TFIIIR, is distinct from the previously identified transcription components: RNA polymerase III, and the accessory factors TFIIIA, TFIIIB, TFIIIC, and TFIIID. The newly discovered TFIIIR is a macromolecule that appears to be composed of RNA. It is resistant to heat, detergent, phenol, protease, and deoxyribonuclease, but it is sensitive to alkali and ribonuclease.
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PMID:A class III transcription factor composed of RNA. 170 25

Different agents have been employed to extract the histones and other soluble components from isolated HeLa S3 nuclei during nuclear matrix isolation. We report that 0.2M (NH4)2SO4 is a milder extracting agent than NaCl and LIS (lithium 3,5-diiodosalicylate), on the basis of the apparent preservation of the elaborate fibrogranular network and the residual nucleolus that resemble the in situ structures in whole cells and nuclei, minimal aggregation, and sufficient solubilization of DNA and histones. The importance of intermolecular disulfide bonds, RNA and 37 degrees C stabilization on the structural integrity of the nuclear matrix was examined in detail using sulfydryl alkylating, reducing and oxidizing agents, and RNase A. The data suggest that any disulfides formed during the isolation are not essential for maintaining the structural integrity of the in vitro matrix. However, structural integrity of the matrix is dependent upon RNA and to some degree on disulfides that presumably existed in situ. Sodium tetrathionate and 37 degrees C stabilization of isolated nuclei resulted in nuclear matrices containing an approximately twofold greater amount of protein, RNA and DNA than control preparations. The 37 degrees C incubation, unlike the sodium tetrathionate stabilization, does not appear to induce intermolecular disulfide bond formation. Neither stabilizations resulted in significant differences of the major matrix polypeptide pattern on two-dimensional (2-D) gels stained with Coomassie Blue as compared to that of unstabilized matrix. The major nuclear matrix proteins, other than the lamins, did not react to the Pruss murine monoclonal antibody (IFA) that recognizes all known intermediate filament proteins, suggesting that the internal matrix proteins are not related to the lamins in intermediate filament-like quality.
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PMID:A comprehensive study on the isolation and characterization of the HeLa S3 nuclear matrix. 171 34

In vitro transcripts from the 3' flanking regions of mustard chloroplast genes were tested for protein binding in a chloroplast extract. Efficient and sequence-specific RNA-protein interaction was detected with transcripts of the genes trnK, rps16 and trnH, but not with the 3' terminal region of trnQ RNA. The transacting component required for specific complex formation is probably a single 54 kDa polypeptide. The protein-binding region of the rps16 3' terminal region was mapped and compared with that of the trnK transcript determined previously. Both regions reveal a conserved 7-mer UUUAUCU followed by a stretch of U residues. Deletion of the trnK 3' U cluster resulted in more than 80% reduction in the binding activity, and after deletion of both the U stretch and the 7-mer motif no binding at all was detectable. RNase protection experiments indicate that the protein-binding regions of both the rps16 and trnK transcripts correlate with the positions of in vivo 3' ends, suggesting an essential role for the 54 kDa binding protein in RNA 3' end formation. In the case of the trnK gene, evidence was obtained for read-through transcripts that extend into the psbA coding region, thus pointing to the possibility of trnK-psbA cotranscription.
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PMID:RNA-protein interactions at transcript 3' ends and evidence for trnK-psbA cotranscription in mustard chloroplasts. 171 78

Insulin-like growth factor (IGF) I is a polypeptide hormone important in normal growth and development. Although IGF-I is a mitogen for many cancer cell lines, previous work has suggested that autocrine production of IGF-I is uncommon in cancers of epithelial origin. In this study, expression of IGF-I, its binding proteins, and its receptor were examined in ovarian cancer cell lines and tissues. Of 10 ovarian cancer cell lines, 3 (OVCAR-3, OVCAR-7, and PEO4) expressed IGF-I mRNA. RNase protection assays using probes derived from IGF-IA, IGF-IB, and alternate exon 1 IGF-I complementary DNAs demonstrated that these cells contained a predominant IGF-I transcript with an alternate first exon. RNA extracted from primary and metastatic ovarian cancer tissues also expressed IGF-I mRNAs (7 of 7) with the alternate first exon. IGF-I protein was detected in OVCAR-3-conditioned media; this activity was secreted in conjunction with several IGF-binding proteins (IGFBPs). IGFBP-2, IGFBP-3, an Mr 24,000 species, and an Mr 30,000 species could also be demonstrated in OVCAR-3. Type I IGF receptor mRNA was found in all 10 of the ovarian cancer cell lines and all 7 of the primary or metastatic ovarian cancer tissues. IGF-I was a mitogen for OVCAR-3, demonstrating the presence of a functional type I IGF receptor. These data show that all the necessary components for an IGF-I-mediated autocrine loop are expressed by ovarian cancer cells.
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PMID:Expression of insulin-like growth factor I, its binding proteins, and its receptor in ovarian cancer. 171 38

We have isolated overlapping cDNA clones from human and hamster libraries which comprise the entire coding sequences for the prepro-alpha 1(V) collagen chains of both species. The translated polypeptide has a signal peptide of 36 amino acids, a central triple helical domain of 338 uninterrupted Gly-X-Y triplets, and 266 amino acids which comprise the C-telopeptide and propeptide. The N-propeptide and telopeptide are comprised of 522 residues in humans and 524 residues in hamsters. The cDNA-derived pro-alpha 1(V) amino acid sequences exhibit a variety of structural features characteristic of fibrillar collagens. Pro-alpha 1(V) is found to be unique among fibrillar collagen chains, however, in lacking potential cross-linking lysyl residues in either telopeptide, and in possessing potential N-asparaginyl-linked carbohydrate attachment sites in its N-propeptide. Of particular interest is the strong homology found between the pro-alpha 1(V) and pro-alpha 1(XI) collagen chains in most domains, with the notable exception of a subdomain in the globular region of the N-propeptide. RNase protection analysis of RNA with a variety of pro-alpha 1(V) cDNA-derived riboprobes indicates a broad distribution of expression of the pro-alpha 1(V) chain in tissues and suggests that transcripts encoding the pro-alpha 1(V) chain and the putative pro-alpha 1'(V) chain are not products of the same gene.
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PMID:The pro-alpha 1(V) collagen chain. Complete primary structure, distribution of expression, and comparison with the pro-alpha 1(XI) collagen chain. 172 13

Angiogenin is a potent blood-vessel-inducing polypeptide with a molecular weight of 14,000 that has a unique ribonucleolytic activity. First isolated from the conditioned medium of tumour cells, angiogenin has since been purified from normal plasma, which suggested that its propensity to induce neovascularization should be strictly controlled. Modulation of that activity might involve interaction of angiogenin with cell-surface receptors and extracellular matrix of endothelial cells, tight-binding inhibition of both its ribonucleolytic activity and cell binding property by ribonuclease inhibitor, as well as the overall influence of divalent copper, a modulator of angiogenesis.
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PMID:In vivo and in vitro studies of angiogenin--a potent angiogenic factor. 172 10

The terminal stage of differentiation of nucleated chicken erythrocytes is associated with an overall gene repression and a condensation of the repressed chromatin portion. Two-dimensional DNP electrophoresis has been used to separate transcriptionally active and repressed chromatin of mature chicken erythrocytes. The repressed chromatin fraction is shown to be enriched with histone H5 as well as with a 42-kDa nonhistone chromosomal protein. The 42-kDa protein designated here as MENT (mature erythrocyte nuclear termination stage-specific protein) is hyperexpressed at the terminal stage of chicken erythropoiesis and is accumulated in adult chicken erythrocyte nuclei. This protein was purified by ion-exchange chromatography from 0.4 M NaCl extracts of the erythrocyte nuclei. It appeared to be a basic polypeptide (pI 9.2) which, however, precipitated at low pH. When reconstituted in vitro with immature erythrocyte nuclei, MENT promoted condensation of intact nuclear chromatin and enhanced the solubilization of nuclease-digested polynucleosomes, thus mimicking the processes occurring in vivo at the final stage of erythrocyte maturation. The extent of dissociation of specific gene sequences from the nuclear matrix in MENT-treated nuclei is in striking correlation with their transcriptional activity. No other basic proteins (H5, cytochrome c, RNase A) added to the nuclear preparation at the same level as MENT (protein/DNA = 0.005) caused any effect on nuclear organization. No alterations were observed when MENT was mixed with erythroblasts and nonerythroid nuclei having little or no histone H5. We propose that MENT cooperates with histone H5 to complete the nuclear collapse in mature nucleated erythrocytes.
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PMID:A novel nonhistone protein (MENT) promotes nuclear collapse at the terminal stage of avian erythropoiesis. 172 33


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