| [photodynamic inactivation of porphyrin sensitized t7 phages: efficiency and mechanism of action]. | we investigated the efficiency and the mechanism of action of two glycoconjugated tetraphenyl porphyrins in their photoreaction with t7 bacteriophage. both types of porphyrins sensitized the photoinactivation of t7, but the slopes of inactivation kinetics were markedly different. our result suggests that both type i and type ii reaction play a role in the virus inactivation. optical melting studies revealed structural changes in the protein part but not in the dna of the photo-chemically treated ... | 2003 | 14702690 |
| photosensitized inactivation of t7 phage as surrogate of non-enveloped dna viruses: efficiency and mechanism of action. | we investigated the efficiency and the mechanism of action of a tetraphenyl porphyrin derivative in its photoreaction with t7 phage as surrogate of non-enveloped dna viruses. tpfp was able to sensitize the photoinactivation of t7 phage in spite of the lack of its binding to the nucleoprotein complex. the efficiency of tpfp photosensitization was limited by the aggregation and by the photobleaching of porphyrin molecules. addition of sodium azide or 1,3-dimethyl-2-thiourea (dmtu) to the reaction ... | 2003 | 14642821 |
| [virus resistance in transgenic watermelon plants containing a wmv-2 coat protein gene]. | virus disease is a major cause that affects the quality and output of watermelon which is an important fruit in summer. so it is really urgent to develop disease resistance plants. but it takes a long time to breed such plants in conventional ways, and it is very difficult to get ideal result. with the development of plant genetic engineering, new ways have been found to breed plants with disease resistance. by using plant transgenic technique, much progress was been made in plant improvement. t ... | 2003 | 12812079 |
| experimental genomic evolution: extensive compensation for loss of dna ligase activity in a virus. | deletion of the viral ligase gene drastically reduced the fitness of bacteriophage t7 on a ligase-deficient host. viral evolution recovered much of this fitness during long-term passage, but the final fitness remained below that of the intact virus. compensatory changes occurred chiefly in genes involved in dna metabolism: the viral endonuclease, helicase, and dna polymerase. two other compensatory changes of unknown function also occurred. using a method to distinguish compensatory mutations fr ... | 2002 | 11861882 |
| an error-prone t7 rna polymerase mutant generated by directed evolution. | viruses replicate their genomes at exceptionally high mutation rates. their offspring evolve rapidly and therefore, are able to evade common immunological and chemical antiviral agents. in parallel, virus genomes cannot tolerate a further increase in mutation rate: experimental evidence exists that even few additional mutations are sufficient for the extinction of a viral population. a future antiviral strategy might therefore aim at increasing the error-producing capacity of viral replication e ... | 2001 | 11828447 |
| synthesis of infectious transcripts of olive latent virus 1: genes required for rna replication and virus movement. | genomic rna of olive latent virus 1 (olv-1) contains five open reading frames (orfs) encoding proteins of 23, 82, 8, 6 and 30 (cp) kda. a full-length cdna copy of olv-1rna was prepared and cloned in a low-copy-number vector (pmuc-19) downstream of or t7 rna polymerase promoter. transcripts derived from this template, denoted pmuc-olv, were highly infectious when inoculated in local and systemic hosts and infected tissues contained virus-like particles. genes required for replication and virus mo ... | 1999 | 10446644 |
| footprinting of chlorella virus dna ligase bound at a nick in duplex dna. | the 298-amino acid atp-dependent dna ligase of chlorella virus pbcv-1 is the smallest eukaryotic dna ligase known. the enzyme has intrinsic specificity for binding to nicked duplex dna. to delineate the ligase-dna interface, we have footprinted the enzyme binding site on dna and the dna binding site on ligase. the size of the exonuclease iii footprint of ligase bound a single nick in duplex dna is 19-21 nucleotides. the footprint is asymmetric, extending 8-9 nucleotides on the 3'-oh side of the ... | 1999 | 10318816 |
| conformation and interactions of the packaged double-stranded dna genome of bacteriophage t7. | the structure of the packaged double-stranded dna genome of bacteriophage t7 was compared to that of unpackaged t7 dna using digital difference raman spectroscopy. spectral data were obtained at 25 degrees c from native t7 virus (100 mg/ml), empty t7 capsids (50 mg/ml), and purified t7 dna (40 mg/ml) in buffer containing 200 mm nacl, 10 mm mgcl2, and 10 mm tris at ph 7.5. at these conditions, the local conformation of t7 dna was not affected by packaging. specifically, the local b-form secondary ... | 1998 | 9787914 |
| ceratobium mosaic potyvirus: another virus from orchids. | a potyvirus, which we call ceratobium mosaic virus, has been detected in about one third of more than 100 plants representing c. 33 orchid genera in two collections in australia. it was detected using rt-pcr with redundant primers that are potyviridae-specific and have additional sequences corresponding to either the sp6 or t7 bacteriophage promoters at their 5'-termini. thus the nucleotide sequence of the resulting pcr fragments, consisting of about 1.7 kb of the 3' portion of the viral genome, ... | 1998 | 9645197 |
| beet yellows closterovirus hsp70-like protein mediates the cell-to-cell movement of a potexvirus transport-deficient mutant and a hordeivirus-based chimeric virus. | it has been suggested that the beet yellows closterovirus (byv)-encoded p65 protein, a homologue of hsp70 cell chaperones, plays a role as a virus movement protein (mp). to test this hypothesis, we used two types of complementation experiments with plant viruses containing the triple gene block (tgb) of mp genes. in one, the byv p65 gene was cloned into a 35s promoter plasmid and introduced into nicotiana benthamiana plants by microprojectile bombardment along with the 35s promoter-driven gus ge ... | 1998 | 9568985 |
| the interaction of plasmid dna with polyamidoamine dendrimers: mechanism of complex formation and analysis of alterations induced in nuclease sensitivity and transcriptional activity of the complexed dna. | the application of synthetic vectors for gene transfer has potential advantages over virus-based systems. however, little is known about the mechanisms involved in binding of synthetic materials to dna and the nature of the dna complexes that result from this interaction. polyamidoamine (pamam) dendrimers are unique polymers with defined spherical structure. dendrimers bind dna to form complexes that efficiently transfect cells in vitro. we examined the formation of dna/dendrimer complexes and f ... | 1997 | 9294012 |
| detection of evolving viruses. | the spread of viruses on a homogeneous lawn of receptive hosts provides an opportunity to detect the dynamics of their evolution. we have previously found that when repeated virus passages are confined to the expanding perimeter of a growing plaque, the appearance and outgrowth of genetically diverse strains (all descended from the same parent strain) can be traced along different radii of the plaque. as a plaque grows, the random mutation and selection of new fast-growing strains reduce the rou ... | 1996 | 9630926 |
| minimized virus binding for tests of barrier materials. | viruses are used to test the barrier properties of materials. binding of virus particles during passage through holes in the material may yield misleading test results. the choices of challenge virus and suspending medium may be important for minimizing confounding effects that might arise from such binding. in this study, different surrogate viruses, as well as different support media, were evaluated to determine optimal test parameters. two membranes with high-binding properties (nitrocellulos ... | 1995 | 7574603 |
| a new hybrid promoter directs transcription at identical start points in mammalian cells and in vitro. | a hybrid promoter which generates large amounts of mrnas with transcription start points (tsp) differing in one nt, both in mammalian cells and in vitro, was constructed by integrating the promoter of bacteriophage t7 in between the tata box and the tsp of the retroviral myeloproliferative sarcoma virus (mpsv) long terminal repeat (ltr). this promoter was designed for sequence and secondary structure studies of 5' untranslated regions (utr) with respect to mrna stability and translatability. | 1994 | 7959028 |
| synthesis of infectious transcripts of blueberry scorch carlavirus in vitro. | blueberry scorch carlavirus (bbscv) is a filamentous virus with a polyadenylated, positive-sense rna genome. a near full-length cdna clone of bbscv was constructed by assembly of clones from a cdna library. to generate a full-length cdna clone, the 5' terminus was mutagenized by pcr to introduce nucleotides present in the wild-type virus and not in the near full-length clone, and then fused directly to the t7 bacteriophage rna polymerase promoter at the 5' terminus. capped and uncapped bbscv tra ... | 1994 | 8077955 |
| nucleotide sequence, genomic organization and synthesis of infectious transcripts from a full-length clone of artichoke mottle crinkle virus. | the complete nucleotide sequence of the genome of artichoke mottle crinkle virus (amcv), a member of the tombusvirus group, has been determined. the genome is 4790 nucleotides (nt) in length. a full-length cdna of the amcv genome has been cloned in puc9 downstream of the t7 rna polymerase promoter. transcripts were infective when inoculated onto nicotiana clevelandii and n. benthamiana plants. the amcv genome contains five open reading frames (orfs). the first orf from the 5' terminus (orf1) enc ... | 1994 | 8021582 |
| the role of dna damage in pm2 viral inactivation by methylene blue photosensitization. | this study investigates the importance of dna damage in viral inactivation by phenothiazines and light. phenothiazines, including methylene blue (mb), toluidine blue and azure b are of particular interest because of their ability to bind to nucleic acids in vitro. initial studies employing phages t7, ms2 and pm2 indicated that both dna and rna phages as well as enveloped and nonenveloped phages can be inactivated by phenothiazine photosensitization. pm2, which contains a lipid-protein bilayer an ... | 1994 | 8041805 |
| virus inactivation by copper or iron ions alone and in the presence of peroxide. | cupric and ferric ions were able to inactivate five enveloped or nonenveloped, single- or double-stranded dna or rna viruses. the virucidal effect of these metals was enhanced by the addition of peroxide, particularly for copper(ii). under the conditions of our test, mixtures of copper(ii) ions and peroxide were more efficient than glutaraldehyde in inactivating phi x174, t7, phi 6, junin, and herpes simplex viruses. the substances described here should be able to inactivate most, if not all, vi ... | 1993 | 8285724 |
| interstrain pseudorecombinants of cowpea chlorotic mottle virus: effects on systemic spread and symptom formation in soybean and cowpea. | full-length complementary dna (cdna) copies of genomic rna1, rna2, and rna3 segments of cowpea chlorotic mottle virus (ccmv) strains d, n, and s were synthesized using polymerase chain reaction and were cloned downstream of a t7 rna polymerase promoter. mixtures of the homologous in vitro-transcribed rnas produced typical ccmv symptoms when inoculated on soybean (cv. bragg) and cowpea (cv. california blackeye) plants. using either gel-purified or in vitro-transcribed ccmv rna components, the pse ... | 2006 | 8118057 |
| infectious rna transcripts derived from cloned cdna of papaya mosaic virus: effect of mutations to the capsid and polymerase proteins. | genomic length cdnas of papaya mosaic virus (pmv) rna were generated utilizing reverse transcriptase (rnase h-) for first strand synthesis, sequenase for second strand synthesis and primers specific for the 5' and 3' termini of the viral genome. these cdnas were cloned into plasmid puc18 and infectious rna transcripts were synthesized in vitro from a bacteriophage t7 rna polymerase promoter incorporated into the 5' specific primer. the infectivity of transcripts was 16% that of native pmv rna. i ... | 1993 | 7685373 |
| in vitro mutagenesis as a result of 60co-gamma-ray-induced base damage. | we utilized a model system to study the mechanism(s) of mutation resulting from gamma-ray-induced dna base damage. 60co-irradiated, uracil-containing m13mp2 dna was hybridized to normal (non-uracil) linearized double-stranded virus dna minus the lac reporter region. only dna without strand breaks in the reporter region will circularize. this dna was used as a substrate for a modified t7 dna polymerase with no residual 3'----5' exonuclease activity (sequenase 2). the reaction product was transfec ... | 1991 | 1720869 |
| construction of a novel rna-transcript-trimming plasmid which can be used both in vitro in place of run-off and (g)-free transcriptions and in vivo as multi-sequences transcription vectors. | we have constructed a new transcription system that allows trimming of both 5' and 3'-termini of any rna transcripts by means of cis-acting ribozyme activities. the vector consists of a promoter, '5' processing ribozyme', any dna template to be transcribed, and '3' processing ribozyme' sequences. when the vector possessing t7 promoter was tested in vitro, the transcription efficiency from the circular template was over ten-fold higher than using linearized template (run-off transcription). furth ... | 1991 | 1923797 |
| in vivo accumulation of a turnip crinkle virus defective interfering rna is affected by alterations in size and sequence. | turnip crinkle virus is one of several single-stranded rna plant viruses associated with defective interfering (di) rnas. a complete cdna copy of a 344-base di rna (di rna g) was cloned downstream from a t7 rna polymerase promoter. transcripts synthesized in vitro were infectious when inoculated with helper virus on turnip plants. studies of the infectivity of di transcripts containing deletions, insertions, and single-base changes suggest that (i) in general, only the 5' two-thirds of the molec ... | 1991 | 1870188 |
| cowpea mosaic virus middle component rna contains a sequence that allows internal binding of ribosomes and that requires eukaryotic initiation factor 4f for optimal translation. | cowpea mosaic virus (cpmv) middle component rna (m-rna) encodes two proteins of 105 and 95 kda, of which translation starts at nucleotide (nt) 161 and nt 512, respectively. in vitro translation of both proteins directed by t7 transcripts of m-rna was stimulated fourfold by eukaryotic initiation factor 4f (eif-4f), the cap-binding protein complex. the ratio of the synthesis of both proteins after translation was not influenced by eif-4f or by any known eif. part of the cpmv 5' sequence was cloned ... | 1991 | 2033661 |
| dye to use with virus challenge for testing barrier materials. | can fd&c blue no. 1 dye photoinactivate bacteriophages phi x174, t7, prd1, and phi 6 under laboratory lighting conditions? at high levels of light, the dye (500 microm) photoinactivated only phi 6. thus, this dye can be used at concentrations up to 500 microm with bacteriophages phi x174, t7, and prd1 to test barrier material integrity. | 1991 | 1872612 |
| red clover necrotic mosaic virus infectious transcripts synthesized in vitro. | the red clover necrotic mosaic dianthovirus (rcnmv) genome is split between two essentially nonhomologous ssrnas of 3.9 kb (rna-1) and 1.45 kb (rna-2) which are each capped at the 5' terminus with m7gpppa. cdna clones short of full length by several nucleotides at both termini have been generated to both rnas. oligonucleotide-directed mutagenesis was employed to generate a series of rna-1 and -2 transcription vectors in which the bacteriophage t7 rna polymerase promoter was fused to full-length ... | 1991 | 2024474 |
| improvements of the infectivity of in vitro transcripts from cloned cowpea mosaic virus cdna: impact of terminal nucleotide sequences. | full-length dna copies of both b- and m-rna of cowpea mosaic virus (cpmv) were constructed downstream from a t7 promoter. by removal of nucleotides from the promoter sequence, b- and m-rna-like transcripts with varying numbers of additional nonviral sequences at the 5' end were obtained upon transcription with t7 rna polymerase. the infectivity of the transcripts in cowpea protoplasts was greatly affected by only a few extra nonviral nucleotides at the 5' end. the addition of about 400 nonviral ... | 1989 | 2596025 |
| avoidance of dna methylation. a virus-encoded methylase inhibitor and evidence for counterselection of methylase recognition sites in viral genomes. | the ocr+ gene of bacterial virus t7 codes for the first protein recognized to inhibit a specific group of dna methylases. the recognition sequences of several other dna methylases, not susceptible to ocr inhibition, are significantly suppressed in the virus genome. the bacterial virus t3 encodes an ado-met hydrolase, destroying the methyl donor and causing t3 dna to be totally unmethylated. these observations could stimulate analogous investigations into the regulation of dna methylation pattern ... | 2006 | 2476230 |
| oligonucleotide duplexes containing cc(a/t)gg stimulate cleavage of refractory dna by restriction endonuclease ecorii. | some dna species are resistant towards the restriction endonuclease ecorii despite the presence of unmodified recognition sites. we show that 14 base-pair oligonucleotide duplexes containing the ecorii recognition site 5'-cc(a/t)gg are cleaved by this enzyme and are able to stimulate ecorii cleavage of such resistant dna molecules (e.g. dna of bacterial virus t3). a direct correlation between the concentration of oligonucleotide duplex molecules and the degree of ecorii digestion of the primaril ... | 1989 | 2784394 |
| use of bacterial virus t7 as a tool for the study of dna methylation. | | 1988 | 3266863 |
| infectious rna transcripts derived from full-length dna copies of the genomic rnas of cowpea mosaic virus. | a set of full-length dna copies of both m and b rna of cowpea mosaic virus (cpmv) was cloned downstream of a phage t7 promoter. upon in vitro transcription using t7 rna polymerase, m and b rna-like transcripts were obtained from these dna copies with only two additional nucleotides at the 5' end and five extra nucleotides at the 3' end in comparison to natural viral rna. in cowpea protoplasts the transcripts of several cdna clones of b rna were able to replicate leading to detectable synthesis o ... | 1988 | 3388776 |
| molecular architecture of bacteriophage t7 capsid. | to determine the capsid structure of bacteriophage t7, we have investigated polycapsids, tubular capsid-related structures isolated from lysates of the t7 mutant am16. biochemical analysis shows polycapsids to be composed of gp10, the major structural protein of the wild-type capsid. the conformational state of gp10 in polycapsids is indistinguishable from that in the mature virus capsid by the criteria of surface charge, buoyant density, and insensitivity to proteolysis by trypsin. optical diff ... | 1983 | 6823742 |
| high resolution sem of bacterial virus t7. | high resolution "low-loss" scanning electron microscopy is a relatively new technique which permits an investigator to examine structures that were formerly visualized exclusively by transmission electron microscopy [1]. this paper presents some images of intact bacterial virus t7, viewed at the ultrastructural level. due to the high resolution capibility of this technique, and the demanding physical prerequisites for visualization of the specimen, current specimen preparation techniques were mo ... | 1979 | 494434 |
| the sex-factor-dependent exclusion of coli virus t7. | the cause of t7 exclusion by the f episome was investigated. extracts from neither normal nor infected f+ cells contained an inhibitor of gene expression in vitro. the protein synthesizing systems prepared in vitro from these cells supported t7 early and late protein synthesis with normal efficiency. the content of translational initiation factors in f- and f+ cells, both noninfected and infected, was almost identical. the episome-dependent block of t7 gene expression was observed only in intact ... | 1975 | 1204611 |
| the physical measurement of radiation damage to coliphage t7 dna. | coliphage t7 was exposed to (60)co gamma radiation while suspended in phosphate buffer or in phosphate buffer plus 0.001 m l-histidine. dna was isolated from the phage by incubation with pronase, followed by extraction with cold phenol. the intrinsic viscosity of the dna was measured as a function of radiation dose. the fraction of dna molecules surviving radiation treatment with no double-strand breaks was measured from the radiation-induced heterogeneity of the dna sedimentation boundary. from ... | 1971 | 5579144 |
| physical properties of the dna from the blue-green algal virus lpp-1. | deoxyribonucleic acid extracted from bgav lpp-1 is double-stranded and has a base composition of 55% guanine plus cytosine. sedimentation analysis indicated that the dna is monodisperse with a molecular weight of 25 +/- 2 million, based on comparison with t7 dna. | 1967 | 18614061 |
| biochemical studies of virus reproduction. xii. the fate of bacteriophage t7. | | 1954 | 13192061 |