Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purpuromycin, an antibiotic active against both fungi and bacteria, shows different modes of action against these two kinds of micro-organisms; in Candida albicans it inhibits RNA synthesis, whereas in Bacillus subtilis protein synthesis is primarily affected, with DNA and RNA synthesis blocked at higher concentrations of the drug. In bacterial cell-free protein-synthesis systems, purpuromycin did not inhibit synthesis from endogenous mRNA (elongation of peptides initiated within the intact cell) but inhibited MS2-phase RNA-dependent protein synthesis (which requires initiation) by 50% at 0.1 mg/l. Poly(U)-directed polyphenylalanine synthesis was 50% inhibited by 20 mg of purpuromycin/l when added to a complete system; however, when purpuromycin was preincubated with ribosomes dissociated into 30 S and 50 S subunits, the concentration for 50% inhibition fell to 0.1 mg/l. By contrast, in a C. albicans cell-free system poly(U)-directed polyphenylalanine synthesis was partially inhibited only at 200 mg/l. Purpuromycin also inhibited polynucleotide synthesis in vitro in reactions using Escherichia coli or wheat-germ RNA polymerases or E. coli DNA polymerase I. We suggest that in bacteria the primary target of purpuromycin is on ribosomes and that its action precedes the elongation step of protein synthesis. The effect on nucleic acid synthesis in both fungi and bacteria may be due to interaction of purpuromycin with DNA.
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PMID:Mechanism of action of purpuromycin. 162 8

Screening of a Mycobacterium tuberculosis genomic DNA library in the lambda gt11 expression vector was carried out by using, as probes, sera from tuberculous patients and murine monoclonal antibody H61.3 recognizing a mycobacterial 35-kilodalton protein present only on the M. tuberculosis complex. The recombinant beta-galactosidase-fused protein present in the crude lysate induced the proliferation of T lymphocytes from patients with tuberculous pleuritis. As the recombinant insert contains an internal EcoRI restriction site, it was possible to identify two fragments, one proximal to the lacZ gene and 1.7 kilobases (kb) in size and the other distal to the lacZ gene and 2.2 kb in size. Southern blot analysis showed that both of them hybridized with the genomic DNA from M. tuberculosis and M. bovis but not with the DNA from other mycobacterial species. To perform extensive immunological studies, the amount of beta-galactosidase-fused protein being very low, we fused the 1.7-kb fragment to the N-terminal part of the gene coding for the DNA polymerase of bacteriophage MS2 in the expression vector pEx34. The fusion protein was partially purified, and subsequent Western blotting (immunoblotting) and T-cell proliferation experiments confirmed the presence of B- and T-cell mycobacterial epitopes. Furthermore, to isolate the chromosomal region containing the 35-kilodalton gene, we constructed another mycobacterial genomic library in the lambda 2001 vector by cloning 15 to 20 kb of foreign DNA. Screening of this library was carried out by using 1.7- and 2.2-kb recombinant fragments as probes. Restriction maps of some clones isolated were determined.
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PMID:Identification of a 35-kilodalton Mycobacterium tuberculosis protein containing B- and T-cell epitopes. 168 20

Expression of the rolB gene of Agrobacterium rhizogenes TL-DNA is sufficient to trigger root differentiation in transformed plant cells. To investigate the role of RolB in differentiation, a large portion of rolB, comprising about 90% of its C-terminal coding sequence, was cloned into vectors pEX34 and pEA305 in frame with the truncated N termini of the pL-MS2 phage DNA polymerase and, respectively, the ptac-c Its phage lambda repressor gene. Hybrid proteins were expressed from both fusions and the one from pMTBEX1 was utilized to raise antibodies. These antibodies specifically recognize the RolB moiety in both pL-MS2-rolB and ptac-cI-rolB fusions. Unfused, complete RolB protein was obtained by in vitro translation in a rabbit reticulocyte system of a transcript obtained by in vitro transcription of rolB. RolB protein is specifically immunoprecipitated by the antibodies raised against the hybrid protein MS2-RolB.
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PMID:Expression of Agrobacterium rhizogenes rolB gene fusions in Escherichia coli: production of antibodies against the RolB protein. 218 36

The 330 residue-long N-terminal domains (NTDs) of beta and beta' subunits of the Escherichia coli RNA polymerase (RPase) core enzyme were found to be significantly homologous to the entire length of its alpha subunit. The C-terminal domains (CTDs) of the RPase beta subunit and DNA primase (dnaG protein) were not only strongly homologous to each other but also considerably homologous to the RPase alpha, suggesting that an alpha subunit-like enzyme must have been commonly ancestral to core enzyme subunits and primase. The N-terminal region (NTR) of RPase alpha was also found to show significant homologies with NTRs of the E. coli EF-Tu and F1-ATPase alpha subunit, and a possible weak homology with ribosomal protein L3. A most important finding was that the C-terminal regions (CTRs) of DNA polymerase (DPase) I, T7 phage DPase and MS2 phage RNA replicase beta subunit are closely homologous with one another. These CTRs showed considerable homologies to RPase alpha NTD and RPase beta CTD. These conclusions are based on statistical evaluations of homologies in base and/or amino acid sequence alignments.
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PMID:Amino acid and nucleotide sequence homologies among E. coli RNA polymerase core enzyme subunits, DNA primase, elongation factor Tu, F1-ATPase alpha, ribosomal protein L3, DNA polymerase I, T7 phage DNA polymerase, and MS2 phage RNA replicase beta subunit. 286 46

Alignment of the amino acid (aa) sequences of T7 phage DNA polymerase (DPase), E. coli DNA polymerase I (Pol I) and MS2 phage RNA replicase beta subunit (MS2 Repl) were established by computer-aided methods. The results showed that the entire length (aa's 16-704) of T7 DPase is homologous to Pol I aa's 207-928(C-term) with 21.5% aa identity, and that domains I (aa's-1-311) and II (312-451(C-term] were found to be homologous to each other and to N-terminal region of T7 DPase (aa's 1-250). Thus these enzymes and domains are homologous to one another and must have evolved from a co-ancestral enzyme.
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PMID:Computer-aided detection and alignment of weakly homologous amino acid sequences of RNA replicase beta (MS2 phage) and DNA polymerases (T7 phage and E. coli). 306 16

Pertussis toxin, a protein composed of five different subunits, is responsible for the pathogenicity of Bordetella pertussis and is the main component of a new vaccine against whooping cough. The genes coding for the five subunits, recently cloned and sequenced, are organized as an operon. We approached the problem of expression of the five genes in Escherichia coli and, although we obtained high levels of transcription of the native pertussis toxin genes, the amount of proteins produced was very low or undetectable. To obtain suitable expression of each of the five subunits, we fused their genes to the gene coding for the DNA polymerase of MS2 in the expression vector pEx31. A total of 5 to 30 mg of purified fusion proteins could be obtained from 1 liter of culture. The purified fusion proteins were used to immunize rabbits to obtain sera against each of the five subunits. These sera, although able to recognize the toxin in an enzyme-linked immunosorbent assay and the corresponding subunits in Western blots, were not able to protect CHO cells from the action of pertussis toxin. Mice immunized with the five subunits were not protected from an intracerebral challenge with B. pertussis. Subunits S2 and S3, which are 67% homologous, were shown to cross-react immunologically. The fused subunit S1 was able to ADP-ribosylate transducin as efficiently as the native pertussis toxin.
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PMID:Expression and immunological properties of the five subunits of pertussis toxin. 354 67

The role of ribonucleic acid (RNA) in deoxyribonucleic acid (DNA) synthesis with the purified DNA polymerase from the avian myeloblastosis virus has been studied. The polymerase catalyzes the synthesis of DNA in the presence of four deoxynucleoside triphosphates, Mg(2+), and a variety of RNA templates including those isolated from avian myeloblastosis, Rous sarcoma, and Rauscher leukemia viruses; phages f2, MS2, and Qbeta; and synthetic homopolymers such as polyadenylate.polyuridylic acid. The enzyme does not initiate the synthesis of new chains but incorporates deoxynucleotides at 3' hydroxyl ends of primer strands. The product is an RNA.DNA hybrid in which the two polynucleotide components are covalently linked. Free DNA has not been detected among the products formed with the purified enzyme in vitro. The DNA synthesized with avian myeloblastosis virus RNA after alkaline hydrolysis has a sedimentation coefficient of 6 to 7S.
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PMID:RNA-dependent DNA polymerase activity of RNA tumor viruses. II. Directing influence of RNA in the reaction. 433 39

In order to identify the reverse transcriptase activity in sera and conditioned media from peripheral blood mononuclear cells (PBMCs) of large granular lymphocyte leukemia patients product enhanced reverse transcriptase activity (PERT) assays were performed using bacteriophage MS2 RNA as a template. All samples obtained from conditioned media of virus-infected cell lines as well as PBMCs of lymphocytic leukemia patients and normal healthy individuals tested positive with this assay. Therefore the validity of the assay was questioned. Careful evaluation of the assay revealed that some of the essential reagents used, such as Taq DNA polymerase and RNase inhibitor contained indigenous amplifiable DNA. DNase I treatment of Taq DNA polymerase before PCR reduced the product significantly. Moreover, no false positive results were observed when encephalomyocarditis virus RNA was used instead of MS2 RNA as the template. These results suggest a need for caution when using bacteriophage MS2 RNA as the template in PERT assays to confirm the presence of retroviral infection or for identification of novel retroviruses.
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PMID:Problems associated with product enhancement reverse transcriptase assay using bacteriophage MS2 RNA as a template. 1271 Oct 64

GLD-2 is a cytoplasmic poly(A) polymerase present in the Caenorhabditis elegans germ line and embryo. It is a divergent member of the DNA polymerase beta nucleotidyl transferase superfamily, which includes CCA-adding enzymes, DNA polymerases and eukaryotic nuclear poly(A) polymerases. The polyadenylation activity of GLD-2 is stimulated by physical interaction with an RNA binding protein, GLD-3. To test whether GLD-3 might stimulate GLD-2 by recruiting it to RNA, we tethered C. elegans GLD-2 to mRNAs in Xenopus oocytes by using MS2 coat protein. Tethered GLD-2 adds poly(A) and stimulates translation of the mRNA, demonstrating that recruitment is sufficient to stimulate polyadenylation activity. We use the same tethered assay to identify human and mouse poly(A) polymerases related to GLD-2. This may provide entrees to previously uncharacterized modes of polyadenylation in mammalian cells.
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PMID:Mammalian GLD-2 homologs are poly(A) polymerases. 1507 Jul 31

The molecular mechanisms of herpes simplex virus (HSV) resistance to antiviral drugs interfering with viral DNA synthesis reported so far rely on the presence of mutations within UL23 (thymidine kinase [TK]) and UL30 (DNA polymerase) genes. The interpretation of genotypic antiviral resistance assay results requires the clear distinction between resistance mutations and natural interstrain sequence variations. The objectives of this work were to describe extensively the natural polymorphism of UL23 TK and UL30 DNA polymerase among HSV-1 and HSV-2 strains and the amino acid changes potentially associated with HSV resistance to antivirals. The sequence analysis of the full-length UL23 and UL30 genes was performed. Ninety-four drug-sensitive clinical isolates (43 HSV-1 and 51 HSV-2) and 3 laboratory strains (KOS, gHSV-2, and MS2) were studied for natural polymorphism, and 25 clinical isolates exhibiting phenotypic traits of resistance to antivirals were analyzed for drug resistance mutations. Our results showed that TK and DNA polymerase are highly conserved among HSV strains, with a weaker variability for HSV-2 strains. This study provided a precise map of the natural polymorphism of both viral enzymes among HSV-1 and HSV-2 isolates, with the identification of 15 and 51 polymorphisms never previously described for TK and DNA polymerase, respectively, which will facilitate the interpretation of genotypic antiviral-resistant testing. Moreover, the genotypic characterization of 25 drug-resistant HSV isolates revealed 8 new amino acid changes located in TK and potentially accounting for acyclovir (ACV) resistance.
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PMID:Genotypic characterization of UL23 thymidine kinase and UL30 DNA polymerase of clinical isolates of herpes simplex virus: natural polymorphism and mutations associated with resistance to antivirals. 2073 37


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