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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The quantity of RNA in the ribosomal fraction of the first leaf of cucumber (Cucumis sativus) increases during growth, reaches a maximum before the final fresh weight is attained, and then decreases. The main changes are in the free ribosome fraction, the quantity of membrane-bound ribosomes remaining about constant. Few 65.5S chloroplast ribosomes are present in small leaves; however, they increase in quantity rapidly during growth and form about half of the ribosomes present in the mature fully green leaf. The cytoplasmic ribosomes have a sedimentation coefficient of 77.6S. Ribonuclease-sensitive polysomes were present in leaves of all ages except possibly the very oldest. The proportion of ribosomes in polysome form decreases during growth and then remains roughly constant during senescence. Following maturation of the leaf, the rate of incorporation of (32)P into ribosomal-fraction RNA begins to decline. This decline could account for the loss of ribosomes during the early stages of senescence. The possibility that leaf ribonuclease might be responsible for the final, more rapid loss of RNA, is discussed.
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PMID:Ribosomes and Polysomes in Cucumber Leaves during Growth and Senescence. 1665 15

RNase activity was assayed in subcellular fractions of apical regions of Pisum sativum L. var. Alaska epicotyls after seedling decapitation and treatments with various growth regulators. High concentrations of applied indoleacetic acid caused a marked increase to occur in the RNase activity level associated with "heavy" microsomes, e.g., a 20-fold rise per unit RNA or protein in 3 days. This rise could be abolished by treating with the cytokinin benzyladenine along with indoleacetic acid. Nevertheless, indoleacetic acid and benzyladenine acted synergistically in their abilities to evoke swelling and net synthesis of RNA and protein. Polysomal profiles prepared after treatment with indoleacetic acid plus benzyladenine showed less degradation than profiles from any other treatment. It is concluded that auxin generates and cytokinin suppresses the activity of a particular membrane-bound RNase which can control turnover of the auxin-evoked polysomes required for growth in peas. Synergism between the two hormones in this system may be explained by the action of one to increase RNA synthesis and the other to decrease RNA destruction.
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PMID:Generation and suppression of microsomal ribonuclease activity after treatments with auxin and cytokinin. 1665 63

Attempts were made to isolate microsomes from Pisum sativum L. var. Alaska by low speed centrifugation of a postmitochondrial supernatant made 8 mm in Ca(2+). However, the addition of Ca(2+) in concentrations as low as 1 mm to the postmitochondrial supernatant resulted in extensive polysome degradation. Degradation was dependent on both Ca(2+) concentration and the duration of incubation. Resuspension of isolated polysomes in Ca(2+)-containing buffer did not result in degradation, whereas resuspension in Ca(2+)-containing postpolysomal supernatant did. Both Ca(2+) and a heat-labile factor in the supernatant were required for polysome degradation. The degradation in the homogenate with or without added Ca(2+) could be reduced by (a) dilution with larger volumes of grinding buffer, (b) increasing the concentration of tris-HCl in the grinding buffer, (c) adding diethylpyrocarbonate or ethyleneglycol-bis (2-aminoethylether) tetraacetic acid (a specific calcium chelator) prior to homogenization or immediately after the addition of Ca(2+). Endogenous Ca(2+) can increase the destruction of polysomes during their isolation in this tissue, presumably by activating a ribonuclease. Addition of Ca(2+) is not a useful technique for separating undegraded free and membrane-bound polyribosomes.
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PMID:Polyribosomes from Peas: III. Stimulation of Polysome Degradation by Exogenous and Endogenous Calcium. 1665 24

Undegraded free and membrane-bound polysomes were isolated from developing kernels of Zea mays L. frozen in liquid nitrogen. Freezing in liquid nitrogen was a prerequisite for preserving polysome structure in stored kernels. Membrane-bound polysomes from 22-day post-pollination kernels ground in high pH buffers containing 50 mm Mg(2+) contained unique classes of large polysomes. These large polysomes were sensitive to ribonuclease, and electron micrographs verified that they were not formed by aggregation. The membrane-bound polysomes were the principal site of zein synthesis, since the major protein synthesized in vitro was similar to purified zein in its ethanol solubility and mobility on sodium dodecyl sulfate polyacrylamide gels.
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PMID:Storage Protein Synthesis in Maize: Isolation of Zein-synthesizing Polyribosomes. 1665 63

Apparent large size-classes of zein-synthesizing polysomes from developing kernels of Zea mays L. were converted to smaller polysomes after treatment with Protease K. The reduction in polysome size was not a result of ribonuclease activity, inasmuch as the enzyme did not affect the free polysomes or the size of the mRNA from the membrane-bound polysomes. High concentrations of MgCl(2) in polysome buffer inhibited ribonuclease activity and appeared to cause protein interaction between nascent zein polypeptides. Although Protease K inhibited the polysome's capacity for protein synthesis, it was a useful reagent for determining if polysomes were aggregated by protein.
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PMID:Dissociation of polysome aggregates by protease k. 1666 Jan 20

The gene FLT1 produces at least two transcripts from a common transcription start site: full-length Flt1 contains 30 exons encoding a membrane-bound VEGF receptor; soluble Flt1 (sFlt1) shares the first 13 exons but utilizes poly(A) signal sequences within intron 13 to create a transcript that lacks downstream exons. To address the mechanisms that regulate human sFlt1, we mapped the 3' end of sFlt1 mRNA and defined the full extent of its 3' untranslated region (UTR). We identified a 3.2 Kb sFlt1 transcript that is cleaved within an alternatively spliced exon downstream of exon 14 and is predicted to encode a C-terminal variant of sFlt1 with an unusual polyserine tail. sFlt1 mRNA cleavage sites within intron 13 were identified in human placenta and in vascular endothelium by ribonuclease protection assay (RPA). A proximal and two distal mRNA cleavage sites were identified by RPA downstream of consensus polyadenylation signals that create variant transcripts with a 3' UTR ranging from 30 bases to approximately 4 Kb. Northern blot analysis and 3' rapid amplification of cDNA ends (RACE) in placenta confirmed the existence of distal intronic sFlt1 cleavage sites that give rise to a sFlt1 transcript of approximately 7 Kb. The identity of the distal signal sequences were then confirmed by mutagenesis of putative signal elements in a polyadenylation reporter assay. We demonstrate the heterogeneity of human sFlt1 that arises from alternate splicing and from alternative polyadenylation directed by strong intronic poly(A) signal sequences leading to C-terminal variants and to an sFlt1 transcript with a large 3' UTR containing several AU rich elements and poly(U) regions that may regulate mRNA stability.
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PMID:Intronic polyadenylation signal sequences and alternate splicing generate human soluble Flt1 variants and regulate the abundance of soluble Flt1 in the placenta. 1761 62

We have used an in vitro labeled, membrane-bound ds[3H]RNA (C. Mouches, C. Bove, and J. M. Bove, 1974, Virology 58, 409-423) to develop a technique by which dsRNA can be detected on glycol methacrylate-embedded ultrathin sections by its resistance to RNase digestion at high but not at low ionic strength. The RNase-resistant ds[3H]RNA is detected on the sections by high-resolution autoradiography. The technique requires that prior to RNase digestion the ultrathin sections be first submitted to a Pronase step. This is accomplished by floating the sections on Pronase (1 mg/ml) for 15 min at 30 degrees , washing the sections three times, and digesting with RNase at high ionic strength for 90 min at 30 degrees . When the washing steps and the RNase hydrolysis are carried out at low ionic strength, dsRNA is completely hydrolyzed. We have applied the Pronase-RNase technique to investigate whether TYMV-specific dsRNA exists in situ after in vivo labeling of the RNAs. [3H]Uridine was fed for 1, 3, and 6 hr through the petiole of healthy or TYMV-infected leaves in the presence or absence of actinomycin D. For a given treatment aliquots of the same leaves were used for three parallel experiments: (1) Araldite embedding for autoradiography; (2) glycol methacrylate embedding for enzyme digestion and autoradiography; and (3) RNA extraction and analysis by polyacrylamide gel electrophoresis. These experiments have shown that after a [3H]uridine absorption by TYMV-infected leaves for 1 hr, in the presence of actinomycin D:dsRNA was the main labeled RNA species seen on the gels; Araldite-embedded sections were labeled specifically at the chloroplast periphery, while glycol methacrylate-embedded sections, submitted to the Pronase-RNase technique to detect dsRNA, were found to contain no dsRNA. Thus replicative intermediate RNA in TYMV-infected cells is essentially single stranded in vivo, and dsRNA is an artifact generated during the RNA extraction procedure.
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PMID:TYMV RNA replication in vivo: replicative intermediate is mainly single stranded. 1863 67

RNase E is an essential endoribonuclease involved in RNA processing and mRNA degradation. The N-terminal half of the protein encompasses the catalytic domain; the C-terminal half is the scaffold for the assembly of the multienzyme RNA degradosome. Here we identify and characterize 'segment-A', an element in the beginning of the non-catalytic region of RNase E that is required for membrane binding. We demonstrate in vitro that an oligopeptide corresponding to segment-A has the propensity to form an amphipathic alpha-helix and that it avidly binds to protein-free phospholipid vesicles. We demonstrate in vitro and in vivo that disruption of segment-A in full-length RNase E abolishes membrane binding. Taken together, our results show that segment-A is necessary and sufficient for RNase E binding to membranes. Strains in which segment-A has been disrupted grow slowly. Since in vitro experiments show that phospholipid binding does not affect the ribonuclease activity of RNase E, the slow-growth phenotype might arise from a defect involving processes such as accessibility to substrates or interactions with other membrane-bound machinery. This is the first report demonstrating that RNase E is a membrane-binding protein and that its localization to the inner cytoplasmic membrane is important for normal cell growth.
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PMID:The RNase E of Escherichia coli is a membrane-binding protein. 1899 Jan 79

Initiation of cell growth and neoplastic transformation frequently involves activation of growth factor receptor-coupled tyrosine kinases and stimulation of the phosphoinositide second messenger system. Altered expression of CD44 variants was reported in several malignant tumor types with possible implications for tumor progression and prognosis. CD44 variant expression was reported to be associated with second messenger activation and differentiation. We therefore investigated the effects of butyrate-induced short-term differentiation on phosphoinositide signaling, phospholipase C and protein kinase C activity and alteration of CD44 variant expression in human HT-29 colon carcinoma cells. HT-29 cells were cultured with sodium butyrate for 6 days. Phosphoinositide turnover was measured by [32P]orthophosphate incorporation and phospholipase C activity by determination of the release of [3H]inositolphosphates from [3H]myoinositol prelabeled cells. Protein kinase C activity was determined by histone III-S phosphorylation, PKC subtype expression by RNase protection analysis, and CD44 variant expression was determined by RT-PCR using variant-specific primers. Treatment of HT-29 human colon carcinoma cells with sodium butyrate caused a dose-dependent inhibition of cell proliferation (IC50, 2.5 mM) with morphologic signs of an enterocytic differentiation following 6 days of treatment. The phosphoinositide turnover as determined by 32P-incorporation under non-equilibrium conditions showed a 30-40% inhibition of labeled phosphoinositides and phosphatidic acid and a dose-dependent inhibition of cholinergically stimulated phospholipase C activity as a secondary event following butyrate-induced enterocytic differentiation. However, long-term incubation of HT-29 cells with phorbol ester or an inhibitor of classical and novel PKC subtypes did not affect cell proliferation. In butyrate-treated HT-29 cells activation of calcium-dependent protein kinase C by cholinergic stimulation or phorbolester treatment induced an increase in membrane-bound cPKC activity, while expression of distinct high- molecular CD44 variant transcripts v3 (670 bp), v5 (940 bp) and v8 (535 bp) were drastically reduced after butyrate pretreatment. Enterocytic differentiation of HT-29 colon carcinoma cells seems to be associated with alterations in phosphoinositide resynthesis, phospholipase C activity and ligand/receptor-induced PKC translocation. The observed reduction of distinct high-molecular CD44v3, v5 and v8 variants following butyrate-induced differentiation indicates an association of specific CD44 variant expression with the malignant phenotype of HT-29 colon cancer cells, thus being possible targets for new diagnostic and therapeutic strategies.
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PMID:Butyrate-induced alterations of phosphoinositide metabolism, protein kinase C activity and reduced CD44 variant expression in HT-29 colon cancer cells. 1936 Mar 23

Small membrane-bound extracellular organelles known as articular cartilage matrix vesicles (ACVs) participate in pathologic mineralization in osteoarthritic articular cartilage. ACVs are also present in normal cartilage, although they have no known functions other than mineralization. Recently, RNA was identified in extracellular vesicles derived from mast cells, suggesting that such vesicles might carry coding information from cell to cell. We found that ACVs from normal porcine and human articular cartilage and primary chondrocyte conditioned media contained 1 microg RNA/80 microg ACV protein. No DNA could be detected. RT-PCR of ACV RNA demonstrated the presence of full length mRNAs for factor XIIIA, type II transglutaminase, collagen II, aggrecan, ANKH and GAPDH. RNA in intact ACVs was resistant to RNase, despite the fact that ACV preparations contained measurable levels of active RNases. Significantly, radiolabeled RNA in ACVs could be transferred to unlabeled chondrocytes by co-incubation and produced changes in levels of chondrocyte enzymes and proteins. The demonstration that ACVs contain mRNAs suggests that they may function to shuttle genetic information between articular cells and indicate novel functions for these structures in articular cartilage.
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PMID:Articular cartilage vesicles contain RNA. 1967


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