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 130,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Infection of rho- Escherichia coli cells with deletion mutant PII of bacteriophage f1 results in a miniphage RNA population composed of transcripts longer than those synthesized in the infection of rho+ cells. This indicates a Rho dependence of the terminator active at the end of the I region of transcription of bacteriophage f1. An estimate of the length of a transcript, which represents a good fraction of the RNA that passes beyond the terminator, indicates that the hairpin structure where synthesis of complementary strand DNA initiates also acts as a fairly efficient Rho-independent terminator.
Mol Gen Genet 1984
PMID:Rho-dependence of the terminator active at the end of the I region of transcription of bacteriophage f1. 609 64

Infection of L929 or BW5147 cells with mumps virus was shown to result in an abortive type of infection in that little or no progeny virus was produced. Both cell lines could adsorb mumps virus, indicating that restricted viral growth in these cells was not attributable to the absence of mumps virus receptors. Using [35S]methionine-labelled virus, it was demonstrated that restriction of virus growth in BW5147 cells was due in part to inefficient virus penetration into the cells. Virus-specific polypeptides were synthesized in mumps virus-infected L929 cells but were not detected in infected BW5147 cells. After addition of actinomycin D or anti-interferon serum to the cultures, mumps virus was able to replicate in L929 cells, whereas no virus growth was apparent in BW5147 cells.
J Gen Virol 1984 May
PMID:Abortive infection of mumps virus in murine cell lines. 620 33

A fragment of the E. coli chromosome including the recC gene has been cloned by in vitro recombinant DNA techniques into a phage lambda vector to give the recombinant phage lambda drecC. This was used to derive the phage lambda drecBC by in vivo recombination. On lysogenisation of recB and recC mutants with lambda drecBC wild levels of UV-resistance and RecBC DNase activity were restored. Infection of E coli with lambda drecBC led to the synthesis of phage-coded proteins of 125 kilodaltons (kd) and 135 kd that were not synthesised on infection with the original lambda vector, whereas a 125 kd protein but not a 135 kd protein was synthesised in similar experiments with lambda drecC. The recombinant phages, which are unable to form plaques, presumably due to the deletion of essential phage genes during their construction, provided useful starting points from which to subclone the recB, recC, and the neighbouring thyA and argA genes individually into multiple copy plasmid vectors.
Mol Gen Genet 1982
PMID:Construction of recombinant lambda phages that carry the E. coli recB and recC genes. 621 90

Membrane preparations from a series of Hfr mutant strains of Escherichia coli K12 deleted in the promoter distal end of the F transfer operon were analyzed. Deletions which extended into traG, as expected, had no discernible effect on synthesis of membrane F-pilin. A more extensive deletion in strain K1777 which eliminated traH activity similarly had no effect on F-pilin synthesis. Membranes from three other TraF+ TraH- deletion strains, as well as membranes from all strains carrying deletions extending into traF or further, lacked F-pilin, however. Since traH amber mutations do not affect synthesis of membrane pilin (Moore et al. 1981 b) we conclude that a gene required for F-pilin biosynthesis is located between traF and traH. We have named this gene traQ. Further evidence for traQ and an assay for its activity was obtained by examining the products of a TraM+ TraJ+ TraA+ lambda transducing phage, KI lambda 13, in UV irradiated cells. Infection of F- cells with KI lambda 13 does not result in F-pilin synthesis. Membrane pilin is synthesized as a product of the transducing phage if an Flac or Hfr irradiated host is used, however. Mutant analysis demonstrated that this synthesis is independent of host expression of traA, traL, traE, traK, traB, traV, traW, traC, traU, traF, or traH, but dependent on expression of the traF-traH region. We interpret our data to indicate that an activity encoded by traQ is required for the conversion of traA product to F-pilin.
Mol Gen Genet 1982
PMID:A new activity in the Ftra operon which is required for F-pilin synthesis. 621 73

Casadaban (1976) developed a technique for isolating E. coli clones containing fusions of the amino terminal-encoding portion of any cistron with the carboxy terminal-encoding portion of lacZ. The technique utilizes prophage Mu homology to bring the two cistrons into proximity. I have followed the appearance over time of colonies containing araB-lacZ fusions from a strain where the beginning of the araB cistron is connected to lacZ by an intact Mucts62 prophage. Cultures of the starting strain grown on a variety of media have fewer than 2 in 10(10) cells capable of forming colonies within three days after plating on selective arabinose-lactose medium. At 32 degrees C, there is a delay of between 4 and 19 days before the first colony appears. The kinetics of colony appearance over the next two to four weeks then shows a rapid increase in the number of new colonies emerging per day followed by a decline. The pattern of colonial emergence and the final numbers of fusion colonies obtained are not grossly affected by reducing the number of cells plated over five orders of magnitude. Fusion colonies sometimes show a clustered pattern when they first emerge. Inoculation of pre-existing fusion clones at specific locations on the arabinose-lactose selection plates seeded with the starting strain leads to the formation of inhibitory zones where no fusion colonies appear. Selection plates contain many microcolonies and papillae which do not proliferate into scoreable colonies but nonetheless contain cells capable of growth when replated on the same selective medium. Up to 39% of all plated cells are capable of producing fusion clones. The kinetics of fusion colony appearance can be altered by environmental and genetic manipulations. Partial derepression of the Mucts prophage at 37 degrees accelerates the appearance of colonies but also reduces the final yield. Addition of limiting concentrations of glucose to the selective medium also accelerates the appearance of colonies in a specific fashion: enrichments below the level required for maximum acceleration produce a biphasic kinetics with two waves of fusion clone emergence separated by an eight-day interval. Infection with Muc+pAp phage produces dilysogens that have almost completely lost the ability to produce fusions. Infection with MuctsAampAp phage produces strains that are reduced in phage production and have delayed kinetics of fusion clone emergence. The implications of these observations for theories of hereditary change in bacteria are discussed.
Mol Gen Genet 1984
PMID:Observations on the formation of clones containing araB-lacZ cistron fusions. 623 72

We demonstrate the use of bacteriophage P4 as a molecular cloning vector in Klebsiella pneumoniae. A hybrid P4 phage, constructed in vitro, that contains a K. pneumoniae hisDG DNA fragment can be propagated either as a lytic viable specialized transducing phage or as an autonomous, self-replicating plasmid. Hybrid P4 genomes existing as plasmids can be readily converted into non-defective P4-hybrid phage particles by superinfection with helper phage P2. Infection of a K. pneumoniae hisD non-P2 lysogen with P4-hisD hybrid phage results in approximately 90% of the infected cells becoming stably transduced to HisD+. Because P4 interferes with P2 growth, high titre stocks of P4 hybrid phages are relatively free (less than or equal to 10(-6) of P2 contamination. The hisG gene product was detected in ultraviolet light irradiated host cells infected by the P4-hisDG hybrid phage. A mutant of P4 (P4sid1) that directs the packaging of P4 DNA into P2 sized capsids should permit the construction of hybrid phages carrying 26 kilobase inserts.
Mol Gen Genet 1980
PMID:Recombinant P4 bacteriophages propagate as viable lytic phages or as autonomous plasmids in Klebsiella pneumoniae. 625 93

Infection of cultures of three different normal rodent cell lines with murine sarcoma virus (MSV) resulted in very rapid loss of contact inhibition of growth and morphological transformation. In the case of two of these lines, anchorage dependence of growth was also rapidly lost but with the 3rd, C3H10T1/2 C1.8, an established line of mouse embryo fibroblasts, there was a delay of many cell generations before the cells became anchorage independent. This was despite 100% successful infection, as assessed by focus assays of the infected cells. The acquisition of anchorage independence was correlated with a substantial increase in tumorigenicity. A number of MSV-infected clones, isolated at random from C3H10T1/2 C1.8 cultures immediately after infection with MSV, also showed a progressive increase in anchorage independence and tumorigenicity, indicating that the progressive transformation of the uncloned cells could not be entirely due to selection of rare anchorage-independent, tumorigenic clones. It was concluded that neoplastic transformation of C3H10T1/2 C1.8 cells by MSV is a multi-step process.
J Gen Virol 1981 Mar
PMID:Neoplastic transformation of mouse fibroblasts by murine sarcoma virus: a multi-step process. 626 40

The xenotropic (X-tropic) mouse type C virus (MuLV) and its pseudotype of murine sarcoma virus (MSV) were inoculated into several fertilized developing Pekin duck eggs. The development of the duck embryos was substantially reduced in those receiving the X-tropic viruses compared to eggs inoculated only with tissue culture medium. Infections virus was isolated from some of the adult animals; in others, evidence for integrated virus sequences in the tissues was noted. No specific pathology was found in the ducks that received X-trophic MuLV alone, but one duck developed multiple fibrosarcomas when inoculated at birth with the X-tropic virus pseudotype of MSV. Two ducks receiving X-tropic MuLv had signs of haematopoietic disorders. In addition, more virus-inoculated animals had evidence of hepatitis and encephalitis than control ducks. Antibody production to X-tropic MuLv was present in several ducks inoculated with virus either in embryo or at birth. Absence of antiviral antibodies was noted in those animals whose tissue contained replicating virus. These studies confirm the observations with X-tropic virus in tissue culture. They demonstrate in vivo that avian species are susceptible to infection by the mouse X-tropic virus and that their fibroblasts can be transformed by the X-tropic MuLV pseudotype of MSV.
J Gen Virol 1982 Jul
PMID:Murine xenotropic type C viruses. IV. Replication and pathogenesis of ducks. 628 52

Infection of CV-1 monkey cells with SV40-GBM, a papovavirus isolated from a human glioblastoma multiforme, resulted in the appearance of defective viral DNA molecules. In contrast to SV40 wild-type, two main types of variant DNA molecules could be found after three viral passages at multiplicities of infection of about 10. The molecules of one variant DNA (GBM3-L) were about 19% shorter than the GBM3-H DNA molecules and the DNA of the original GBM isolate, as demonstrated by electron microscopy. Restriction enzyme analysis revealed that GBM3-L DNA had lost both the EcoRI and the HpaII cleavage sites which are located in the late viral genome region. Furthermore, SV40 GBM3-L did not possess the two PvuII sites which are located in the late genome region, and a portion of the GBM3-H and GBM3-L DNA molecules had lost the unique KpnI site. Heteroduplex analysis verified that the rearrangements in the GBM3-L DNA are located only in the late region of this DNA. The possible differences between SV40 wild-type and SV40-GBM are discussed on the basis of these results.
J Gen Virol 1983 Mar
PMID:Studies on the SV40-like papovavirus SV40-GBM. I. Genomic analysis by restriction endonucleases and electron microscopy after propagation in CV-1 monkey cells. 629 54

The synthesis of virus polypeptides in rat XC cells infected with herpes simplex virus type 1 (HSV-1; 13VB4tsC75) was studied. At the permissive temperature the virus induced the synthesis, in a cascade fashion, of significant amounts of several early polypeptides (ICP 6, 8 and 39) and those late polypeptides that are relatively resistant to inhibition by phosphonoacetic acid in HEp2 cells (ICP 5, 11, 25, 29, 43 and 44). The infectious cycle appeared to become arrested in XC cells at about 7 to 9 h postinfection, because the relative concentrations of early and latest polypeptides labelled thereafter remained constant and the levels of several of the late virus polypeptides were severely reduced (ICP 2, 10, 24 and 26) or not synthesized at all (ICP 32, 34 and 37). When XC cells were infected at a very high m.o.i., only a small amount of virus DNA synthesis could be detected; the synthesis of cellular DNA was not impaired and the infected XC cells continued to replicate for several weeks at least. When XC cells were infected at the non-permissive temperature, only the immediate-early (IE) ICP 4 could be detected while IE ICP 0 and 22 were not observed. Infection of XC cells with HSV-1 (MP) also resulted in the production of early and late viral polypeptides. On the other hand, in XC cells infected with HSV-1 (F) and HSV-1 (HFEM), the synthesis of virus polypeptides could not be detected.
J Gen Virol 1983 Jul
PMID:Virus polypeptide synthesis induced by herpes simplex virus in non-permissive rat XC cells. 630 50


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