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:3.1.30.1 (S1 nuclease)
3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The T4 molecule (CD4) is an important component of the human immunodeficiency virus (HIV) receptor. As yet, no other component has been demonstrated. We report here that two cell lines, a B lymphoblastoid cell line (Gupta) and a glial cell line (HEB) derived from human embryonal brain tissue, are productively infectable with two distinct isolates of HIV as judged by electron microscopy and immunological and virological studies. These two cell lines do not display detectable surface CD4 glycoprotein. However, using S1 nuclease analysis, we have found that both cell lines do express low levels of CD4 mRNA. Neither of them produced syncytia formation upon HIV infection, a recognized feature of HIV-infected cells strongly expressing the CD4 glycoprotein. It is conceivable that the CD4 mRNA is translated, resulting in meager surface expression of CD4 molecules undetectable by conventional techniques. Therefore, infection with HIV may be one of the most sensitive methods of demonstrating low levels of CD4 expression by human cells. Furthermore, HIV-infected Gupta cells have here been shown to be more susceptible to the lytic activity of natural killer (NK) cells than their uninfected counterparts. These phenomena may be important for pathogenesis of HIV-associated disorders.
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PMID:Infection of B lymphocytes by the human immunodeficiency virus and their susceptibility to cytotoxic cells. 290 61

Genomic DNA clones containing the gene coding for the 20-kDa T3 glycoprotein of the T-cell receptor/T3 complex (T3-delta chain) of human and mouse were isolated and characterized. The human T3-delta gene is approximately equal to 4 kilobases (kb) long and contains five exons: a 151-base-pair (bp) exon containing the 5' untranslated and the coding sequences of the signal peptide, one exon of 219 bp, which contains most of the extracellular segment of the T3-delta chain, one 130-bp-long exon coding mainly for the transmembrane portion of the molecule, and two exons of 44 bp and 156 bp encoding the cytoplasmic domain and 3' untranslated region of the T3-delta chain, respectively. The murine T3-delta gene, which has a similar organization, contains 5 kb, because the first intron is approximately equal to 1 kb larger than in the human gene. Two major mRNA initiation sites within a small area approximately equal to 100 nucleotides 5' of the AUG codon were determined by S1 nuclease analysis and primer-extension studies. The remarkably high level of conservation of nucleotide sequences in this region suggests that this segment may be important for the regulation of T-cell-specific transcription of the T3-delta gene. The T3-delta gene does not contain the "TATA box" found in many eukaryotic promoters.
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PMID:Exon/intron organization of the genes coding for the delta chains of the human and murine T-cell receptor/T3 complex. 293 61

The Ly-5 system of the mouse is expressed exclusively by hematopoietic cells and comprises a series of glycoprotein isoforms that typify different hematopoietic cell lineages. The 200-kDa isoform of T cells and the 220-kDa isoform of B cells are known to differ in peptide composition. The complete 1152 amino acid sequence of the 200-kDa isoform protein deduced from cDNA sequence appears to comprise a leader sequence of some 30 residues, an external N-terminal domain of 370 residues, a probably single transmembrane domain of 22 residues, and an unusually large cytoplasmic domain of 730 residues. Both the external and cytoplasmic domains include regions of internal homology suggestive of evolution from a smaller ancestral gene. RNA transfer blotting has previously shown that B-cell mRNA for Ly-5 is larger than T-cell mRNA. S1 nuclease protection mapping with Ly-5 cDNA probes suggests that this difference can be ascribed to interpolation of an extra B-cell sequence located at the 5' end of B-cell mRNA, probably immediately following the leader sequence. From restriction mapping of overlapping Ly-5 genomic clones spanning 60 kilobases it is concluded that Ly-5 isoforms are generated by differential processing of transcripts of a single gene, rather than from a family of linked Ly-5 genes.
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PMID:Sequences of Ly-5 cDNA: isoform-related diversity of Ly-5 mRNA. 294 16

From a genomic DNA library of Sendai virus, we have identified and sequenced clones corresponding to the F glycoprotein gene. The limits of the F gene region were defined by mapping the 5' and 3' ends of the mRNA with S1 nuclease. The Sendai virus F gene is 1821 nucleotides long. The predicted primary translation product of the single long open reading frame would code for a protein of 565 amino acids, containing a putative signal peptide, three carbohydrate addition sites, a hydrophobic region corresponding to the known cleavage/activation site of FO, and a long, very hydrophobic region near the C-terminus which probably represents the transmembrane region of the protein. The signal peptide cleavage site of the mature protein was determined by mass spectrometry. Interestingly, the amino acid sequence surrounding the cleavage/activation site of the Sendai virus F protein shows significant homology to the same region of the influenza B and C virus HA proteins, suggesting that these genes may have evolved from a common ancestor. The ability of the Sendai virus F protein to fuse membranes relative to its primary structure is discussed.
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PMID:Sequence determination of the Sendai virus fusion protein gene. 298 71

The non-telomeric variant surface glycoprotein (VSG) genes in Trypanosoma brucei are activated by a duplicative transposition to a telomeric expression site. We have determined the 5' end of the transposed segment of the gene for VSG 117 and infer from comparison with similar data obtained by others that the crossover can occur at variable positions within short repeats present upstream of this gene and in the expression site. We have analysed nascent and steady state transcripts of the transposed gene and its neighbouring expression site DNA. The results indicate that transcription starts upstream of the transposed gene segment in the expression site and that transcripts are rapidly processed at specific points identified by protection of DNA-RNA hybrids against digestion by nuclease S1 or Exo VII. Hence, this gene appears to be activated by a process akin to promoter addition.
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PMID:Transcription of a transposed trypanosome surface antigen gene starts upstream of the transposed segment. 300 50

A rapid technique involving the S1 nuclease resistance of RNA:DNA duplexes has been used to screen four Trypanosoma equiperdum variant surface glycoprotein (VSG) genes for evidence of hybrid gene structure in their transcribed regions. The results suggest that VSGs appearing early in a chronic infection each have a complete co-linear basic copy (BC) of their expressed gene while VSGs appearing later in infection are particularly associated with BC genes which are recombined before being expressed. The intensities of the S1-protected bands from hybrid VSGs indicate that the basic and expression linked copies are present in equivalent gene dosages. In addition, studies are presented on the expression of two additional VSG genes in T. equiperdum, VSG 4 and VSG 78, which (i) show that the basic copies are not located on telomeres even though one (VSG 4) is expressed early in infection and (ii) emphasize the role of a predominant expression site in T. equiperdum while nevertheless confirming the presence of multiple expression sites.
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PMID:Expression of whole and hybrid genes in Trypanosoma equiperdum antigenic variation. 301 13

An S1 nuclease preparation was used to purify the enzyme to homogeneity. The enzyme had an isoelectric point of 4.2, and a high content of hydrophobic amino acids, especially tyrosine. It exhibited low 3'-ribonucleotidase activity. Circular dichroism analysis suggested that the contents of alpha-helix, beta-structure and random coil are 25%, 31% and 44%, respectively. The enzyme contained about 3 g atoms Zn/mol and the removal of Zn from the enzyme by addition of EDTA resulted in disruption of its secondary structure with resultant inactivation. From Con A-Sepharose chromatography, we suggest that the enzyme is a high-mannose glycoprotein. After treatment with endo-beta-N-acetylglucosaminidase H under moderate conditions, a small part of the enzyme was converted to a form lacking the sugar side chain. This form of the enzyme was as thermostable as the parent enzyme, suggesting that the sugar side chain may not be involved in thermostability of the enzyme.
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PMID:Purification of S1 nuclease to homogeneity and its chemical, physical and catalytic properties. 302 Dec 29

Earlier reports have localized mutations which affect the processing and transport of herpes simplex virus 1 glycoproteins to a region located between the genes specifying glycoprotein B and the major viral DNA-binding protein (beta 8). The nucleotide sequence of this region contains a single long open reading frame encoding a 780-amino-acid protein with a predicted molecular weight of 83,845. To confirm the existence of this protein, rabbit polyclonal antibody was made against a synthetic peptide made according to the predicted sequence of a hydrophilic domain near the carboxy terminal of the protein. This antibody reacted with an infected cell protein of an apparent molecular weight of 95,500. We designated this protein infected cell protein 18.5 (ICP18.5). S1 nuclease analysis suggested that the 5.6-kilobase mRNA encoding ICP18.5 is initiated predominantly from one site, but three weaker initiation sites also seemed to occur within a 74-base-pair stretch of DNA. This gene appears to be conserved in the Epstein-Barr virus (EBV) genome, inasmuch as 174 of the 780 amino acids of ICP18.5 align with corresponding amino acids predicted by the EBV open reading frame BALF3. The EBV gene is located adjacent to the gene specifying a homolog of the herpes simplex virus 1 glycoprotein B.
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PMID:Transcription initiation sites and nucleotide sequence of a herpes simplex virus 1 gene conserved in the Epstein-Barr virus genome and reported to affect the transport of viral glycoproteins. 302 64

The gene encoding the beta-subunit of rat thyrotropin (TSH beta) has been isolated and characterized. Blot hybridization of restriction enzyme digests of rat genomic DNA suggests that the gene is present in a single copy. The transcriptional unit is 4.9 kilobases in size representing 3 exons interrupted by 2 introns of 3.9 and 0.4 kilobases. Its nucleotide sequence reveals that the locations of the exon/intron junctions are one nucleotide upstream from the translational start and between codons +34 and +35. The location of the second intron is apparently strictly conserved among the glycoprotein hormone beta-subunit genes being four codons downstream from a region encoding a consensus sequence: Cys-Ala-Gly-Tyr. Using S1 nuclease mapping and oligonucleotide-primed reverse transcription of normal and thyroidectomized rat pituitary mRNA, two transcriptional start sites were identified in the rat TSH beta gene that are 28 and 71 nucleotides upstream from the translational start site. The level of TSH beta mRNA containing the downstream site is altered by thyroidal status whereas the other mRNA utilizing the upstream cap site appears to be constitutively expressed. Characteristic promoter elements are present in the 5'-flanking region including TATAAA or Goldberg-Hogness consensus regions which are present 29 and 26 bases upstream from the respective starts of transcription. Also, several CAAT boxlike sequences are located between 95 and 300 bases upstream from the start of translation. Isolation and characterization of the gene encoding the TSH beta gene will facilitate the study of the molecular mechanisms by which hormones regulate TSH beta gene expression.
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PMID:Isolation and characterization of the rat thyrotropin beta-subunit gene. Differential regulation of two transcriptional start sites by thyroid hormone. 302 91

Previous inferences that Ly-5 glycoprotein isoforms of murine hematopoietic cells are generated by alternative splicing of primary transcripts of a single Ly-5 gene are supported by the present study. A cDNA library was prepared from B cells by extension from primer representing a known T-cell cDNA sequence. Three different Ly-5 clones from this library included sequences missing in T-cell cDNA clones. From the constitution of cDNA clones and of the Ly-5 gene, and from S1 nuclease mapping, it is concluded that at least two exons, provisionally numbered Ex-6(B) and Ex-7(B), in the 5'-proximal region are mainly represented in mRNA of the B-cell lines examined but not of the T-cell lines examined. Also, exons 1 and 2 appear to be used alternatively in different species of B-cell mRNA and probably also in different species of T-cell mRNA.
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PMID:Alternative use of 5' exons in the specification of Ly-5 isoforms distinguishing hematopoietic cell lineages. 303 46


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