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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)

The variant-specific surface glycoprotein (VSG) gene 221 of Trypanosoma brucei is transcribed as part of a 60 kb expression site (ES). We have identified the promoter controlling this multigene transcription unit by the use of 221 chromosome-enriched DNA libraries and VSG gene 221 expression site specific transcripts. The start of transcription was determined by hybridization and RNase protection analysis of nascent RNA. The 5' ends of the major transcripts coming from the initiation region map at nucleotide sequences that do not strongly resemble rRNA transcriptional starts even though the transcripts are synthesized by an RNA polymerase highly resistant to alpha-amanitin. The cloned VSG gene 221 ES transcription initiation region promotes high CAT gene expression, when reintroduced by electroporation into T. brucei. We show that the activity of this expression site is controlled at or near transcription initiation in bloodstream trypanosomes. The 221 ES is inactivated without any sequence alteration within 1.4 kb of the transcription start site. This excludes mechanisms of promoter inactivation involving DNA rearrangements in the vicinity of the transcription start site, e.g. promoter inversion or conversion.
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PMID:The promoter for a variant surface glycoprotein gene expression site in Trypanosoma brucei. 169 65

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

Using synthetic oligonucleotide probes, we have cloned a genomic DNA sequence encoding a ribonuclease (RNase) T2 gene (rntB) from Aspergillus oryzae on a 4.8 kb HindIII fragment. DNA sequence analysis of the RNase T2 revealed the following: (1) The gene is arranged as five exons and four introns; (2) The deduced amino acid sequence contains 239 amino acid residues of the mature enzyme. In addition, there exist 17 amino acid residues thought to be a signal peptide sequence at the N-terminus and 20 amino acid residues at the C-terminus; (3) The nucleotide sequence of the rntB gene is homologous to those of the RNase Rh gene from Rhizopus niveus and the S2 stylar glycoprotein gene of Nicotiana alata with degree of about 51% and 47%, respectively; (4) A. oryzae and A. nidulans transformed with the cloned rntB gene had much higher ribonuclease T2 activity than wild-type strains.
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PMID:Cloning and nucleotide sequence of the genomic ribonuclease T2 gene (rntB) from Aspergillus oryzae. 191 76

The primary structure of nuclease P1, which cleaves both RNA and single-stranded DNA, from Penicillium citrinum was elucidated. The complete amino acid sequence consisting of 270 residues was determined by analysis of peptides obtained by digestion with Achromobacter protease I of the reduced and S-aminoethylated protein and by digestion with Staphylococcus aureus V8 protease of the reduced and S-carboxymethylated protein. Four half-cystine residues were assigned to Cys72-Cys217 and Cys80-Cys85. N-Glycosylated asparagine residues were identified at positions 92, 138, 184 and 197. Fast-atom-bombardment and laser-ionization MS were successfully used to confirm the determined amino acid sequences of peptides and to estimate the molecular mass of this glycoprotein having heterogenous sugar moieties, respectively. Comparison of the amino acid sequence of nuclease P1 with other nucleases revealed that the protein has a high degree of sequence identity (50%) with nuclease S1 from Aspergillus oryzae. The His-Phe-Xaa-Asp-Ala sequence (positions 60-64) is similar to the sequence (His-Phe-Asp-Ala) involving the active-site His119 of bovine pancreatic RNase A, and the Pro-Leu-His sequence (positions 124-126) is identical with the sequence involving the active-site His134 of porcine pancreatic DNase I.
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PMID:Primary structure of nuclease P1 from Penicillium citrinum. 191 39

Two neutral ribonucleases have been purified from developing tomato fruit. Their activity is maximal 5 days after anthesis, declines during maturation, and then increases slightly in the mature green through breaker stages. The ribonucleases Tf1 and Tf2 have molecular weights of 59 and 29 K, respectively, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and are glycoproteins. The reduced and denatured Tf1 is composed of two subunits, 30 and 29 K, of which only the 30-K subunit displays ribonuclease activity after renaturation. Reduced and denatured Tf2 is a single 29-K polypeptide that is renaturable to an active ribonuclease. Only the 30-K, active subunit of Tf1 is immunologically cross-reactive with Tf2. Both ribonucleases are cyclyzing endoribonucleases with a strong preference for cleavage at pyrimidine residues, thus generating oligonucleotide products ending with pyrimidine 2',3'-cyclic phosphate. These tomato fruit ribonucleases share a number of properties in common with the S-glycoprotein ribonucleases that are involved in self-incompatibility reactions in some solanaceous plants.
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PMID:Purification and characterization of two ribonucleases from developing tomato fruit. 192 99

Thrombospondin (TSP) is a trimeric glycoprotein which is synthesized and incorporated into the extracellular matrix by a wide variety of cells. TSP is involved in a number of cellular processes which govern tumor cell behavior including mitogenesis, attachment, migration, and differentiation. To directly assess the role of TSP in tumor cell growth and spread, a human squamous carcinoma cell line, with high TSP production and an invasive phenotype, was transfected with a TSP cDNA antisense expression vector. Five unique transfected clones were obtained with reduced TSP production. Expression of the transfected antisense sequence in these clones was verified by a ribonuclease protection assay. These clones demonstrated reduced growth rates in vitro when compared with a vector transfected control. After subcutaneous inoculation into athymic mice, the antisense clones formed either no tumors or tumors that were slow growing and highly differentiated. This contrasted with the vector-transfected clone which produced poorly differentiated, rapidly growing, invasive tumors. Our results argue in favor of a direct role for TSP in determining the malignant phenotype of certain human tumors.
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PMID:Antisense-mediated reduction in thrombospondin reverses the malignant phenotype of a human squamous carcinoma. 204 Jun 84

The isolation and determination of biological activities of the active component of Corynebacterium kutscheri were attempted in the present investigation. The antitumor effect was confined to the subcellular particle fraction of this bacterium and was associated with a molecule of glycoprotein nature (40,000-38,000 Daltons) isolated from this fraction by affinity chromatography with concanavalin A-Sepharose 4B. This substance exerted mitogenic activity on C3H/HeJ splenocytes and T cells, stimulatory activity on macrophages, and further exhibited antitumor effect on P388 leukemia in CDF1 mice. The Winn assay disclosed that the antitumor effect induced by this substance was dependent on L3T4+ T cells. Furthermore, both the mitogenic and antitumor activity of this moiety were resistant to heating at 100 degrees C for 30 min or RNase digestion, but sensitive to trypsin digestion, or low or high pH. These results indicate that the antitumor effect of C. kutscheri is attributable to the heat-stable glycoprotein moiety which can directly stimulate T cells and macrophages.
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PMID:Nonspecific stimulation of host defense by Corynebacterium kutscheri. II. Isolation of the active moiety. 208 46

A TSH receptor (TSH-R) cDNA has been isolated from a human thyroid lambda GT11 library. Unexpectedly, several cDNAs encoding the human LH/CG receptor (LH/CG-R), previously thought to be expressed solely in gonadal cells, were also isolated from the thyroid library. The receptors are structurally related, consisting of a signal sequence, a large extracellular amino terminal domain, seven membrane spanning domains, and a short carboxyl-terminal portion. The TSH-R is encoded by a single 4.2 kilobase mRNA specific to the thyroid. Introns were not present in any hTSH-R cDNAs examined, however, sequencing of several LH/CG-R cDNAs and RNase protection experiments demonstrated that the majority of hLH/CG-R mRNA in the thyroid is incompletely spliced. Consequently, tissue-specific splicing may be an important step in the regulation of the glycoprotein hormone receptor family.
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PMID:Isolation of TSH and LH/CG receptor cDNAs from human thyroid: regulation by tissue specific splicing. 229 30

The glycoprotein (GP) IIb/IIIa heterodimer functions as a receptor for fibrinogen, von Willebrand factor, and fibronectin on activated platelets; it is dysfunctional in the bleeding diathesis Glanzmann's thrombasthenia. This receptor is a member of the integrin family, which includes homologous membrane receptors involved in a number of different cell-cell and cell-matrix adhesive interactions. Knowledge of the sequence and organization of the GPIIb and GPIIIa genes will help in understanding evolutionary relationships and functional homologies of this family of adhesion protein receptors and will facilitate analysis of molecular defects responsible for thrombasthenia. Using the GPIIb cDNA as a probe, we have isolated overlapping genomic clones encompassing the entire coding region, the 5'- and 3'-untranslated sequences, and the immediate flanking regions for the GPIIb gene. The gene spans approximately 17.2 kilobases (kb); all but approximately 2.6 kb of intronic DNA sequence has been determined. The GPIIb gene contains 30 exons whose demarcations do not correlate with previously suggested functional domains. Two intron/exon borders have the rare GC splice donor sequence instead of the consensus GT sequence. There are at least seven complete and three partial AluI sequence repeats within the intron sequences. RNase protection, S1 nuclease analysis, and primer extension studies using human erythroleukemia (HEL) cell RNA and platelet RNA map a major transcription start site 32 base pairs (bp) 5' to the beginning of the coding region; however, there are no canonical consensus TATA or CAAT boxes in the region immediately 5' to the proposed cap site. The immediate 5'-flanking sequence of rodent GPIIb demonstrates complete identity near the proposed cap site with its human counterpart, but again, no TATA or CAAT boxes are apparent.
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PMID:Organization of the gene for platelet glycoprotein IIb. 232 58

A ribonuclease has been isolated from human spleen (RNase HS) by means of acid extraction, ammonium sulphate fractionation, successive column chromatographies on CM-cellulose, heparin-actigel, and poly(G)-agarose, and double gel-filtration on Sephadex G-75. The purified preparation was homogeneous as judged by SDS/PAGE. RNase HS was found to be a glycoprotein, containing three fucose, one mannose and five glucosamine residues/molecule, with a molecular mass of 17 kDa as determined by both SDS/PAGE and gel filtration. The catalytic properties and structural features, including its amino acid composition and the amino acid sequence of the N-terminal 35 residues, indicated that the enzyme was strictly related to nonsecretory RNase isolated from human urine and liver. In particular, the amino acid sequence of the N-terminal was identical with that of urine nonsecretory RNase and eosinophil-derived neurotoxin. Furthermore, analyses using three different antibodies specific to RNase HS, urine nonsecretory RNase and urine secretory RNase, indicated that RNase HS was not immunologically distinguishable from urine nonsecretory RNase, but clearly so from urine secretory RNase. However, the carbohydrate compositions of RNase HS and urine nonsecretory RNase were found to differ. It therefore remains to be resolved whether or not the tissue of origin of nonsecretory RNase in urine is the spleen.
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PMID:Purification and characterization of a ribonuclease from human spleen. Immunological and enzymological comparison with nonsecretory ribonuclease from human urine. 238 98


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