Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Earlier, we reported a 30-200-fold reduction in the yield of infectious vesicular stomatitis virus (VSV) released from L cells treated with 10-30 reference units ml-1 of interferon (IFN); however, in these cultures virus particle production, as measured by VSV particle-associated viral RNA, virus nucleocapsid protein and viral transcriptase, was inhibited less than 10-fold. There was biochemical and morphological evidence of a significant reduction in glycoprotein (G) and membrane protein (M) of VSV particles released from IFN-treated cells. We compare here the effects of tunicamycin (TM) and IFN in L cells. Treatment with TM or IFN reduced the production of infectious VSV particles, decreased the amount of G and M proteins in VSV released from treated cells, and inhibited an early step in the formation of asparagine-linked oligosaccharide chains, the incorporation by membrane preparations from treated cells of N-acetylglucosamine into glycolipids with the properties of dolichol derivatives.
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PMID:Interferon treatment inhibits glycosylation of a viral protein. 615 39

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal defect of hematopoietic stem cells in which affected cells are characterized by the lack of glycosylphosphatidylinositol (GPI)-anchored proteins. The lesion in PNH lies in the defective synthesis of N-acetyl-D-glucosaminyl-phosphatidylinositol (GlcNAc-Pl), the first intermediate in GPI biosynthesis. Reintroduction of the PIG-A gene into GPI(-) patient cells reportedly complements this defect. We have analyzed here PIG-A transcripts of six PNH patients. GPI+ and GPI- cell lines from each individual were used, ie, Epstein-Barr virus-transformed B-lymphoblastoid cell lines, T-cell lines, and natural killer cell clones. Reverse transcriptase polymerase chain reaction and sequencing showed three different PIG-A splicing variants in GPI+ cell lines, in which the largest transcript contained the wild-type PIG-A coding region sequence. GPI-deficient cell lines showed abnormal splicing variants. Sequencing of PIG-A complementary DNA and genomic DNA showed heterogeneous mutations ranging from different point mutations to small deletions. Two lymphocyte cell lines (T- and B-cell lines) of one patient presented with the same mutation. For another patient, two different mutations were detected in one natural killer cell line. Therefore, different cell lineages have somatic mutations in PIG-A that lead to PNH.
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PMID:Heterogeneous PIG-A mutations in different cell lineages in paroxysmal nocturnal hemoglobinuria. 788 83

The largest high-glycosylated domain, glycopeptide A, of the "insoluble' mucin complex of the rat small intestine has earlier been purified and characterized (Carlstedt et al., 1993, J Biol Chem 268: 18771-81). A rabbit antiserum raised against deglycosylated glycopeptide A was used to clone part of a mucin showing homology to the human MUC2 mucin (Hansson et al., 1994, Biochem Biophys Res Commun 198. 181-90). This serum specifically stained goblet cells (paranuclear) in the mouse small intestine. The size of the coding sequence of glycopeptide A was estimated by using reversed transcriptase PCR of mRNA from an inbred rat strain (GOT-W) using primers in the unique central and C-terminal parts of the proposed rat Muc2 sequences. The PCR and Southern blot of the PCR products showed a fragment of about 5.5 kb corresponding to about 1700 amino acids when the known Cys-rich sequences used for the primers were subtracted. This is slightly larger than the size estimated earlier by biochemical studies. The mRNA encoding the rat Muc2 was slightly smaller than the mRNA encoding the human MUC2 in a colorectal cell line. Although the size of glycopeptide A estimated from biochemical results and by PCR is not identical, the results obtained here further support that the "insoluble' mucin of the rat small intestine is encoded by the Muc2 gene. Most of the oligosaccharides in glycopeptide A were either neutral (40%) or sialylated (40%). The remaining ones were sulfated with the sulfate group attached to C-6 of N-acetylglucosamine linked to C-6 of the N-acetylgalactosaminitol as revealed by tandem mass spectrometry of the perdeuteroacetylated oligosaccharides. Eighteen oligosaccharides were found of which fourteen were characterized and found to be mostly novel. Our findings thus expand the current knowledge of the core peptide of the rat intestinal goblet cell mucin and provide a relatively complete picture of the glycosylation of a defined mucin domain.
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PMID:Molecular characterization of the large heavily glycosylated domain glycopeptide from the rat small intestinal Muc2 mucin. 891 9

We have characterized an operon required for inner-core biosynthesis of the lipooligosaccharide (LOS) of Neisseria meningitidis. Using Tn916 mutagenesis, we recently identified the alpha-1,2-N-acetylglucosamine (GlcNAc) transferase gene (rfaK), which when inactivated prevents the addition of GlcNAc and alpha chain to the meningococcal LOS inner core (C. M. Kahler, R. W. Carlson, M. M. Rahman, L. E. Martin, and D. S. Stephens, J. Bacteriol. 178:1265-1273, 1996). During the study of rfaK, a second open reading frame (lgtF) of 720 bp was found upstream of rfaK. An amino acid sequence homology search of the GenBank and EMBL databases revealed that the amino terminus of LgtF has significant homology with a family of beta-glycosyltransferases involved in the biosynthesis of polysaccharides and O antigen of lipopolysaccharides. The chromosomal copy of lgtF was mutagenized with a nonpolar antibiotic resistance cassette to minimize potential polar effects on rfaK. Tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis and composition analysis of the LOS from the nonpolar lgtF mutant showed that this strain produced a truncated LOS structure which contained a LOS inner core of GlcNAc1Hep2KDO2lipid A but without the addition of lacto-N-neotetraose to HepI or glucose to HepII. These results and the amino acid homology with beta-glycosyltransferases suggest that lgtF encodes the UDP-glucose:LOS-beta-1,4-glucosyltransferase which attaches the first glucose residue to HepI of LOS. Reverse transcriptase PCR and primer extension analysis indicate that both lgtF and rfaK are cotranscribed as a polycistronic message from a promoter upstream of lgtF. This arrangement suggests that completion of the LOS inner core and the initiation of the alpha chain addition are tightly coregulated in N. meningitidis.
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PMID:Two glycosyltransferase genes, lgtF and rfaK, constitute the lipooligosaccharide ice (inner core extension) biosynthesis operon of Neisseria meningitidis. 895 82

Mice with a null mutation in the Mgat1 gene lack N-acetyl-glucosaminyltransferase I (GlcNAc-TI; EC 2.4.1.101), and die at mid-gestation. This result suggested that development of Mgat1-/- blastocysts and their implantation could occur in the absence of complex and hybrid N-glycans. However, inner cell mass of all blastocysts from several Mgat1 +/- heterozygous crosses bind the lectin E-PHA, indicating that Mgat1 null mutant blastocysts are able to synthesize complex N-glycans (Campbell et al., (1995) Glycobiology, 5, 535-543). In order to directly test this hypothesis, Mgat1-/- blastocysts were positively identified by polymerase chain reaction (PCR) of genomic DNA. Reverse transcriptase PCR (RT-PCR) of RNA isolated from the same blastocysts, and restriction analysis of the PCR products, revealed that Mgat1 null blastocysts contained Mgat1 RNA derived from the wild-type Mgat1 gene. Consistent with this, all 3.5 day blastocysts from five heterozygous crosses bound the lectin L-PHA, a lectin previously shown not to bind to E8.5 or E9.5 Mgat1-/- embryos that lack complex N-glycans (Ioffe and Stanley (1994) Proc. Natl. Acad. Sci., USA, 91, 728-732). Blastocysts of 4.5 days postcoitum (dpc) obtained by culturing 3.5 dpc blastocysts also bound L-PHA. However, mutant embryos that did not bind L-PHA were present among progeny from E5.5 onward. Therefore, the effects of the Mgat1 null mutation are not operative until sometime between implantation and E5.5, due to the continued presence of maternally derived Mgat1 mRNA in preimplantation embryos.
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PMID:Complex N-glycans in Mgat1 null preimplantation embryos arise from maternal Mgat1 RNA. 936 33

We studied the beta-1,3-galactosyltransferase (GalT) and alpha-1,2-fucosyltansferase (FT) involved in the biosynthesis of type-1-chain carbohydrate antigens in human colon adenocarcinoma cell lines. We detected a GalT activity able to use GlcNAc as acceptor and found that lacto-N-biose I (Galbeta1-3GlcNAc) is the only reaction product. Such beta1,3GalT is kinetically similar to a pig trachea enzyme involved in mucin synthesis. The specific activity is high in cells that react strongly with anti-Lewis a and anti-Lewis b antibodies, and undetectable in a cell line that lacks antibody reaction. Reverse-transcriptase-mediated PCR analysis followed by DNA sequencing indicated that secretor-type alpha1,2FT is expressed in the cells, while the H type alpha1,2FT is not. The apparent Km values for donor and acceptor substrates determined for alpha1,2FT are similar to those of secretor-type alpha1,2FT and the specific activity measured correlates with Lewis b antigen expression on the cell surface. Moreover, some of the cell lines express Lewis y and H type 2 antigens, indicating that secretor type alpha1,2FT is responsible for their synthesis. Results suggest that biosynthesis of type-1-chain tumor-associated antigens in human colon carcinoma cells is operated by secretor-type alpha1,2FT, as reported in normal mucosa, and that beta1,3GalT activity may play a relevant role in its control.
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PMID:Beta-1,3-galactosyltransferase and alpha-1,2-fucosyltransferase involved in the biosynthesis of type-1-chain carbohydrate antigens in human colon adenocarcinoma cell lines. 976 Jan 91