bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical modification of simian virus 40 DNA by reaction with a water-soluble carbodiimide
Authors: Lebowitz J , Garon C G , Chen M C , Salzman N P
Published: January 2020

Superhelical simian virus 40 (SV40) DNA I can be modified with N-cyclohexyl-N'-beta-(4 methylmorpholinium)ethylcarbodiimide (CMC). The reaction produces an increase in the sedimentation velocity of DNA I from 21 to 22.5S and a decrease in its buoyant density in CsCl from 1.694 to 1.688. A comparable shift in buoyant density is observed in a saturated ethidium bromide-cesium chloride gradient where form II, which has been exposed to CMC, shows no shift. The CsCl-buoyant density data allows us to estimate that 108 mol of CMC are bound per mol of SV40 DNA I. In the subsequent paper an alternative procedure has been used to locate CMC sites, and the extent of the regions available to bind CMC have been measured.
Process of infection with bacteriophage phi chi 174. XL. Viral DNA replication of phi chi 174 mutants blocked in progeny single-stranded DNA synthesis
Authors: Fukuda A , Sinsheimer R L
Published: January 2020

Mutation in several different cistrons of bacteriophage phi chi 174 blocks net progeny single-stranded DNA synthesis at the late period of infection (15). For the study of the functions of these cistrons in single-stranded DNA synthesis, asymmetric replication of replicative form DNA was examined at the late period of infection with amber mutants of these cistrons. While the normal, rapid process of asymmetric single-stranded viral DNA synthesis is blocked at the late period of these mutant infections, an asymmetric synthesis of the viral strand of replicative-form DNA is observed in this period, though at a reduced level, together with degradation of prelabeled viral strand. Some intermediate replicative-form molecules were also detected. Asymmetric synthesis of the viral strand of replicative-form DNA at the late period of phi chi infection is completely inhibited in the presence of a low concentration (35mug/ml) of chloramphenicol (which also blocks net single-stranded viral DNA synthesis). These results are discussed in terms of the possible role of the specific viral proteins for normal single-stranded DNA synthesis.
Isolation and partial characterization of a corynebacteriophage beta, tox operator constitutive-like mutant lysogen of Corynebacterium diphtheriae
Authors: Murphy J R , Skiver J , McBride G
Published: January 2020

We have isolated and partially characterized a beta-phage mutant lysogen of Corynebacterium diphtheriae, C7(betatoxct1+), which is partially insensitive to iron inhibition of diphtheria toxin production. tox expression by C7(betatoxct1+) was found to be partially constitutive. In the presence of concentrations of iron that almost completely inhibit the expression of diphtheria toxin by the wild type, C7(beta), the level of toxin production by C7(betatoxct1+) was found to be at least 25 times that of the parent. The purified tox gene product of C7(betatoxct1+) was immunologically and electrophoretically identical to, and equally as toxic as, diphtheria toxin purified from C7(beta). In addition, the partial N-terminal amino acid sequence was found to be identical to diphtheria toxin. This data strongly suggests that the mutation allowing for the constitutive expression of tox in C7(betatoxct1+) is outside of the structural gene. Furthermore, the constitutive expression of diphtheria toxin was found to be cis dominant in the double lysogen C7(betacrm45+/betatoxct1+). The data presented is consistent with the existence of a tox operator locus.
Mechanism of interaction of avian myeloblastosis virus reverse transcriptase with avian myeloblastosis virus RNA
Authors: Yamaura I , Cavalieri L F
Published: January 2020

The synthesis of DNA on avian myeloblastosis virus (AMV) RNA as the primer-template using AMV reverse transcriptase in vitro has been examined as a function of the concentrations of these components, as well as a function of the ionic strenth of the assay medium. The results are consistent with the hypothesis that two types of sites exist on the AMV RNA: inactive "dead-end" sites that merely bind the enzyme, and active binding sites that lead to DNA synthesis. Velocity sedimentation studies of reverse transcriptase reveal that the enzyme becomes a dimer (or oligomer) at low salt concentrations and it is at these concentrations that the two types of sites are evident on the RNA. At high salt concentration the enzyme, which exists primarily as a monomer, is inactive with AMV RNA, although it is active when poly(rA)dT10 is used as the primer-template. We have shown that inactive sites are not due to binding of the reverse transcriptase to nicked regions or to partially denatured RNA molecules. We deduce that inactive sites are those containing incorrect 4S primer molecules. These results are discussed in terms of the mechanism of the interaction of the reverse transcriptase with AMV RNA.
Deoxyribonucleoside triphosphate pools in synchronized human cells infected with herpes simplex virus types 1 and 2
Authors: Roller B , Cohen G H
Published: January 2020

Deoxyribonucleoside triphosphate pools in uninfected and herpes simplex virus type 1 (HSV-1)- and HSV-2-infected KB cells were analyzed to determine whether ribonucleotide reductase functions in vivo in the presence and absence of thymidine (TdR). Previously we showed that HSV-2 replication was inhibited in KB cells blocked in their capacity to synthesize DNA by TdR. HSV-1 replication was not inhibited under these conditions. Both HSV-1 and HSV-2 induced an altered ribonucleotide reductase resistant to dTTP inhibition. Thus, the block to HSV-2 replication apparently was not at the level of reductase. However, the in vitro activity of the enzyme does not necessarily correspond to intracellular conditions. In TdR-blocked HSV-2-infected cells, we found that, while dTTP levels remained high, dCTP concentrations increased. In contrast, KB cells blocked by TdR showed increased dTTP but decreased dCTP levels. We conclude that the HSV-2 enzyme is functional in vivo and that TdR inhibits viral replication by a mechanism other than depletion of dCTP. Infection of KB cells with HSV-1 or HSV-2 altered both dATP and dGTP levels in the presence or absence of TdR. Inhibition of viral replication was not explained by changes in these pools. We suggest that, during infection, HSV-1 induces a virus function(s) not related to reductase which is resistant to TdR, whereas the corresponding HSV-2 function is sensitive. Our evidence shows that the TdR-sensitive function is not in the pathways leading to deoxyribonucleoside triphosphate and may occur at the level of DNA replication.
Fate of input oncornavirion RNA--biological studies
Authors: Sveda M M , Fields B N , Soeiro R
Published: January 2020

The fate of input Friend leukemia virus RNA was studied using labeled input virus. The appearance of nuclear RNA-DNA hybrid molecules and the apparent integration of input virion RNA with host cell DNA was studied using a series of inhibitors of DNA or protein synthesis, cell growth conditions, and an intercalating agent. Under all these conditions of infection, little to no viral-specific RNA-DNA hybrid molecules were formed. These data demonstrate that the formation of such RNA-DNA hybrid structures requires conditions of infection that allow provirus synthesis and integration. Furthermore, they suggest that at least a fraction of input virion RNA may transiently become integrated with host cell DNA.
Further characterization of the Friend murine leukemia virus reverse transcriptase-RNase H complex
Authors: Moelling K
Published: January 2020

The purified reverse transcriptase-RNase H complex from Friend murine leukemia virus consists of a single polypeptide of 84,000 molecular weight, which after mild protease treatment in vitro or after intentional degradation during the purification procedure allows the generation of several additional polypeptides. Degradation destroys the RNA-dependent DNA polymerase activity with native RNA templates and reduces RNase H but does not affect response to synthetic template primers such as poly (rA)-Oligo (dT). The properties of the intact murine enzyme consisting of a single polypeptide of 84,000 molecular weight are compared to those of the avian alpha subunit and the avian alpha beta enzyme complex. The intact murine enzyme resembles the avian beta-containing enzyme complex and is different from alpha in the following respects: (i) it binds to native RNA templates; (ii) it transcribes native RNA templates into DNA, a reaction which can be inhibited by actinomycin D; (iii) RNase H activity behaves like a processive exonuclease; and (iv) analysis of the RNase H digestion products reveals oligonucleotides approximately four bases in length.
Fractionation of DNA nucleotide transcripts from Moloney sarcoma virus and isolation of sarcoma virus-specific complementary DNA
Authors: Frankel A E , Neubauer R L , Fischinger P J
Published: January 2020

Radioactive DNA complementary to nucleotide sequences in Moloney murine sarcoma virus (MSV) and Moloney leukemia virus (M-MuLV) complex was made by the endogenous reverse transcriptase reaction. These virus stocks contained a threefold excess of MSV over M-MuLV as measured by biological assay. The complementary DNA was an accurate copy of the viral RNA in that 86% of 35S viral RNA hybridized with complementary (cDNA) DNA at a 1.5 to 1 cDNA-RNA molar ratio. The complementary DNA, of a 4-6S size, was fractionated by sequential absorptions with MulV and the feline leukemia virus pseudotype of MSV, [MSV(FeLV)] RNA. In this manner three sets of nucleotide sequences whichrepresent different portions of the MSV viral complex were obtained: a sarcoma virus-specific fraction (cDNAsarc) with sequences that had no homology to M-MuLV RNA but which hybridized to MSV (FeLV) RNA, a sarcoma-leukemia fraction (cDNA common) with sequences common to MSV as well as M-MuLV viral RNA, and a cDNAleuk representing those nucleotide sequences found only in M-MuLV. Hybridization of MSV-MuLV viral 35S RNA with a threefold molar excess of cDNA's revealed that approximately 20% was hybridized with cDNAsarc, whereas approximately 75% was hybridized with cDNAcommon. M-MuLV 35S RNA alone did not hybridize with cDNAsarc but did hybridize 40 and 50% with cDNAleuk and cDNAcommon, respectively. The cDNAsarc represents about 25% of the total MSV sequences, whereas the cDNAcommon represents the remainder of the MSV virus genome. Some cDNAcommon sequences were shared by two other sarcoma viruses and several distinctly different isolates of MulV. In contrast, the MSV "sarc" sequences had little or no homology with two other murine sarcoma virus isolates.
Deletion mapping of moloney type C virus: polypeptide and nucleic acid expression in different transforming virus isolates
Authors: Parks W P , Howk R S , Anisowicz A , Scolnick E M
Published: January 2020

The viral polypeptides and viral RNA present in cells transformed by various replication-defective type C viruses derived from Maloney murine leukemia virus were examined. Different portions of the Maloney type C viral genome were retained in the different transforming viruses, thus providing an opportunity for deletion mapping of the Moloney type C genome. DNA transcripts were prepared that are complementary to three distinct nonoverlapping portions of the Moloney viral geonome. Based on an anlysis of the polypeptides produced in the different transformed cells, one complementary DNA apparently respresents sequences coding for Moloney gp70; one complementary DNA represents a region of the Moloney genome common to all of the transforming viruses examined, and one complementary DNA represents the sequences for p30, p15, p10,12. A partial map of the different replication-defective transforming viruses is suggested.
Inhibition of pseudorabies virus replication by vesicular stomatitis virus. II Activity of defective interfering particles
Authors: Dubovi E J , Youngner J S
Published: January 2020

Purified defective interfering (DI) particles of vesicular stomatitis virus (VSV) inhibit the replication of a heterologous virus, pseudorabies virus (PSR), in hamster (BHK-21) and rabbit (RC-60) cell lines. In contrast to infectious B particles of VSV, UV irradiation of DI particles does not reduce their ability to inhibit PSR replication. However, UV irradiation progressively reduces the ability of DI particles to cause homologous interference with B particle replication. Pretreatment with interferon does not affect the ability of DI particles to inhibit PSR replication in a rabbit cell line (RC-60) in which RNA, but not DNA, viruses are sensitive to the action of interferon. Under similar conditions of interferon pretreatment, the inhibition of PSR by B particles is blocked. These data suggest that de novo VSV RNA or protein synthesis is not required for the inhibition of PSR replication by DI particles. DI particles that inhibit PSR replication also inhibit host RNA and protein synthesis in BHK-21 and RC-60 cells. Based on the results described and data in the literature, it is proposed that the same component of VSV B and DI particles is responsible for most, if not all, of the inhibitory activities of VSV, except homologous interference.
Identification of the gene controlling the synthesis of the major bacteriophage T5 membrane protein
Authors: Duckworth D H , Dunn G B , McCorquodale D J
Published: January 2020

After infection of Escherichia coli B by bacteriophage T5, a major new protein species, as indicated by polyacrylamide gel electrophoresis, appears in the cells' membranes. Phage mutants with amber mutations in the first-step-transfer portion of their DNA have been tested for their ability to induce membrane protein synthesis after they infect E. coli B. We have found that phage with mutations in the Al gene of T5 do not induce the synthesis of the T5-specific major membrane protein, whereas phage that are mutant in the A2 gene do induce its synthesis. We conclude that gene Al must function normally for T5-specific membrane protein biosynthesis to occur and that only the first 8% (first-step-transfer piece) of the DNA need be present in the cell for synthesis to occur.
Comparative properties of bacteriophage phi6 and phi6 nucleocapsid
Authors: Etten J V , Lane L , Gonzalez C , Partridge J , Vidaver A
Published: January 2020

Nonionic detergent treatments released a nucleocapsid from the enveloped bacteriphage phi6. The nucleocapsid sedimented at nearly the same rate as the whole phage in sucrose density gradients, but the buoyant density in Cs2S04 changed from 1.22 g/cm3 for the whole phage to 1.33 g/cm3 for the nucleocapsid. The detergent completely removed the lipid and 5 of the 10 proteins from the phage. Surface labeling of the phage and nucleocapsid with 125I revealed that protein P3 was on the outer surface of the whole phage and P8 was on the surface of the nucleocapsid. Both the phage and the nucleocapsid were stable between pH 6.0 and 9.5. Low concentrations of EDTA (10-4 M) dissociated the nucleocapsid but had no effect on the whole phage. The nucleocapsid contained all three double-stranded RNA segments, as well as RNA polymerase activity.
Properties of the scrapie agent-endomembrane complex from hamster brain
Authors: Semancik J S , Marsh R F , Geelen J L , Hanson R P
Published: January 2020

Subcellular fractionation of scrapie-infected hamster brain indicated the association of the scrapie agent with a component of the endomembrane system. Characterization by equilibrium density gradient centrifugation, electron microscopy, and marker enzymes suggested a primary association with rough and smooth endoplasmic reticulum and a possible incorporation into the plasma membrane. DNA polymerase activity demonstrated a direct correlation with regions of scrapie activity from the gradient fractions. A scrapie-related product was detected after (3H)TMP incorporation and analysis on 2.2% polyacrylamide gels. Analysis of nucleic acid species extracted from subcellular fractions resulted in a greater quantity from healthy brain; however, no qualitative distinctions were detected.
Spontaneous Release of Endogenous Ecotropic Type C Virus from Rat Embryo Cultures
Authors: Rasheed Suraiya , Bruszewski Joan , Rongey Robert W. , Roy-Burman Pradip , Charman Howard P. , Gardner Murray B.
Published: January 2020

Type C viruses were isolated from embryo cultures of two different rat strains, Sprague-Dawley and Fischer. Both viruses (termed rat leukemia virus, RaLV) were released spontaneously from rat embryo cells, have a density of 1.14 to 1.15 g/cm
3
based on equilibrium sedimentation in sucrose gradients, contain 60-70
S
RNA, RNA-directed DNA polymerase, and rat type C virus-specific 30,000 molecular-weight-protein determinants. Molecular hybridization studies using the Sprague-Dawley RaLV 60-70
S
RNA show that the virus-specific nucleotide sequences are present in the DNA of rat embryos. Both Sprague-Dawley and Fischer RaLV can rescue the murine sarcoma virus genome from Kirsten murine sarcoma virus-transformed nonproducer cells and are neutralized by antisera to the RPL strain of RaLV. In contrast to previous RaLV's, these viruses propagate in their own cells of origin as well as in cells of heterologous rat strains.
Preliminary biochemical characterization of the factors(s) responsible for herpesvirus-induced exogenous fusion
Authors: Levitan D B , Blough H A
Published: January 2020

Cell-free extracts prepared from herpes simplex virus-infected BHK-21 cells rapidly induced exogenous fusion when incubated with indicator monolayers of uninfected BHK-21 cells. Fusion was first observed at 1 h, and peak activity was reached by 4 h. Divalent cations were required for activity. Inhibition of indicator cell macromolecular synthesis, with metabolic inhibitors, failed to prevent formation of cell-free extract-induced polykaryocytes. Removal of virus particles from the cell-free extract by velocity sedimentation centrifugation did not affect cell-free extract exogenous fusion activity. Studies using molecular probes, namely, glycosidases, lectins, and antiserum (directed against either HSV envelope or capsid proteins), suggest that the factor(s) responsible for herpesvirus fusion is a fucosylated glycoprotein that is not a structural component of the virion.
In vitro synthesis of A-particle structual protein by membrane-bound polyribosomes
Authors: Lueders K K
Published: January 2020

On the basis of association with endoplasmic reticulum membranes, poyribosomes isolated from mouse myeloma MOPC-104E were separated into two classes, membrane bound and free. The membrane-bound and free polyribosomes were then compared for their capacity to incorporate [35S]methionine into A-particle proteins in vitro. As revealed by a radioimmunological assay method, labeling of A-particle protein occurred with the membrane-bound polyribosomes but not with the free polyribosomes. Peptide mapping of the immunoprecipitated, in vitro [35S]methionine-labeled product confirmed that A-particle protein had been synthesized in vitro.
Leukemia virus infection of mammalian cells: effect on two "transformation-associated" surface properties
Authors: Noonan K D , Wright P J , Bouck N , Di Mayorca G
Published: January 2020

We demonstrated that the productive infection of three different mammalian cell lines with two separate leukemia viruses is sufficient to induce a change in surface architecture that may be detected as enhanced agglutinability with two different plant lectins. Subsequent transformation of one of these cell lines with a chemical carcinogen did not further modify the agglutinability of the cell lines. Using a polyoma virus-transformed derivative of one of the parental lines, we have demonstrated that the LETS protein (whose absence from the surface membrane has been considered a marker of the transformed phenotype) may be present in cells displaying the capacity to plate in soft agar.
Collaborative Study of Temperature-Sensitive Mutants of Herpes Simplex Virus Type 2
Authors: Timbury Morag C. , Hendricks Mary Lee , Schaffer Priscilla A.
Published: January 2020

Eighteen complementation groups were identified by complementation tests and by phenotype from twenty temperature-sensitive mutants isolated independently in Glasgow, Scotland, and Houston, Tex.
Infectious center assay for complementation and recombination between mutant of reovirus
Authors: Spandidos D A , Graham A F
Published: January 2020

An infectious center assay has been developed to measure recombination and complementation in L cells mixedly infected with ts mutants of reovirus. The mutants studied so far fall into complementation groups that correspond to the recombination groups previously defined by other laboratories (B. N. Fields, 1971; B. N. Filds and W. K. Joklik, 1969).
Intracellular restriction on the growth of induced subgroup E avian type C viruses in chicken cells
Authors: Robinson H L
Published: January 2020

Subgroup E avian type C viruses produced by bromodeoxyuridine-treated 100 X 7, line 7, or line C chicken cells were restricted in their intracellular growth on K28 chicken cells but not on line 15 chicken cells. Cells from embryos of line 15 chickens bred with K28 chickens did not restrict the growth of the subgroup E induced leukosis viruses (ILVs). This result indicates that the phenotype for the intracellular restriction of the growth of subgroup E ILVs found in K28 cells is recessive. Long-term growth of the subgroup E ILVs in K28 cells resulted in the appearance of subgroup E virus that grew well on K28 cells. No change in growth characteristics was observed for subgroup E ILVs grown in line 15 cells indicating that appearance of nonrestricted virus occurred only during growth of the subgrouo E ILVs on a restrictive host. RAV-0, a subgroup E virus closely related to the ilvs, had the same growth characteristics as the subgroup E ILVs. RAV-60, a subgroup E virus formed by recombination of exogenous avian leukosis virus with endogenous subgroup E virus coat information, grew well on both line 15 and K28 cells.
Mechanism of release of active alpha subunit from dimeric alpha beta avian myeloblastosis virus DNA polymerase
Authors: Papas T S , Marciani D J , Samuel K , Chirikjian J G
Published: January 2020

Storage of the dimeric (alphabeta) form of avian myeloblastosis virus (AMV) DNA polymerase in glycerol resulted in the release of the smaller alpha subunit, as detected by glycerol gradient sedimentation. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of enzyme stored in glycerol showed the concomitant appearance of several polypeptides and a lowering in the level of both beta and alpha components. This reduction appears to be the result of cleavages introduced by traces of hydrolytic activity present in glycerol samples. An enhancement of alpha subunit released, as detected by activity profile, was also achieved upon direct but limited exposure of purified avian myeloblastosis virus DNA polymerase to carboxymethyl-cellulose-bound trypsin matrix. Electrophoretic analysis of digested enzyme revealed a progressive fragmentation, with simultaneous increase in the alpha subunit and decrease in the beta subunit.
Early synthesis of Semliki Forest virus-specific proteins in infected chicken cells
Authors: Kaluza G
Published: January 2020

Cells preinfected with fowl plague virus followed by treatment with actinomycin D are a suitable system for studying early protein synthesis in cells infected with Semliki forest virus. One and one-half hours after superinfection, three new nonstructural proteins (NVP) were detected: NVP 145, NVP, 112, and NVP 65. They appeared in parallel with a low incorporation of mannose at the beginning of the infectious cycle. Behavior on chasing suggested a precursor relationship of NVP 112 to the envelope glycoproteins. Two kinds of NVP 65 are described, both of which are varieties of NVP 68 with an incomplete mannose content. One type, detected early after infection, was converted into NVP 68 by supplementary glycosylation. The second, late type was stable. It contains fucose and resembles the NVP 65 observed after impairment of glycosylation. The mechanism of NVP 68 glycosylation is discussed. The presence of the complete carbohydrate moiety is crucial for the cleavage of NVP 68 into the envelope proteins E2 and E3 and, thus, for virus maturation. Only the complete form of NVP 68 was precipitated by envelope-specific antisera. A large production of NVP 78 is a further feature of the early events in infected cells. It is not related to the structural proteins.
Origin of the phospholipids of a lipid-containing virus that replicates in Escherichia coli: bacteriophage PR4
Authors: Sands J A
Published: January 2020

Bacteriophage PR4 contains lipid and can reproduce in strains of Escherichia coli that carry an appropriate drug-resistance plasmid. Cultivated in either of two E. coli strains, PR4 acquires a lipid region that contains a relatively high level of phosphatidylglycerol and significant amounts of three phospholipids, including phosphatidylserine, which are present in only very low levels in the host cell membranes. To do this, however, PR4 does not significantly alter the relative levels of synthesis of the various E. coli phospholipids after infection. Production of PR4 virions from E. coli cultures labeled with 32PO4 either before or after infection showed that about two-thirds of the viral phospholipid is synthesized after infection. The use of E. coli as the host organism for PR4 should allow a detailed understanding of the assembly process of this lipid-containing virus due to the wealth of biochemical and genetic techniques available.
Enzymatic degradation of uracil-containing DNA. II. Evidence for N-glycosidase and nuclease activities in unfractionated extracts of Bacillus subtilis
Authors: Duncan J , Hamilton L , Friedberg E C
Published: January 2020

Further studies have confirmed our earlier observations that in the presence of EDTA, degradation of phage PBS2 [3H]uracil-labeled DNA is effected by an N-glycosidase activity in extracts of Bacillus subtilis that removes free uracil from DNA. In addition, such extracts contain a nuclease activity that attacks PBS2 DNA in the presence of CaCl2. The nuclease activity is not observed under conditions that inactivate N-glycosidase activity but does attack DNA that has been preincubated to remove uracil by N-glycosidase action. We therefore postulate that the nuclease requires N-glycosidase action to generate substrate for its activity, i.e., the nuclease appears to attack depyrimidinated sites rather than uracil sites in phage PBS2 DNA.
Isolation and characterization of a heat-inducible simian virus 40 mutant
Authors: Rothschild H , Lockwood M P
Published: January 2020

We have isolated a new type of temperature-sensitive mutant of simian virus 40 (SV40) that is capable of productive infection in permissive cells but not of maintenance of viral DNA integration in transformed cells at the conditional temperature. Virus development is induced when cells transformed by this mutant are shifted to temperatures above 39 degrees C, but is not induced below this temperature. The plaque-purified, temperature-sensitive mutant virus confers heat inducibility to new host cells, indicating that the conditional function is a property of the viral genome. Unlike previously described temperature-sensitive SV40 mutants, in (ts)-1501 is capable of productive infection in permissive cells at the conditional temperature. The morphology, growth, and oncogenicity of in (ts)-1501-transformed cells at 37 degrees C are similar to those of cell lines transformed by wild-type SV40. HK10-c2(in(ts)-1501), a cloned cell line, transformed at 37 degrees C by the mutant virus, exhibits a transient increase in DNA synthesis before cell death at the conditional temperature. Many properties of in(ts)-1501 are analogous to those of the heat-inducible mutants of bacteriophages in which a heat-inactivated protein is responsible for the stable integration of the prophage in the bacterial chromosome.
Failure of defective interfering particles of Sindbis virus produced in BHK or chicken cells to affect viral replication in Aedes albopictus cells
Authors: Igarashi A , Stollar V
Published: January 2020

Whereas defective interfering particles of Sindbis virus are readily produced in BHK-21 cells or chicken embryo fibroblasts by the techniques of serial undiluted passage, similar methods failed to generate such particles in Aedes albopictus cell cultures. In addition, Sindbis virus stocks produced in BHK-21 cells or chicken embryo fibroblasts and which contained defective interfering particles, when tested in A. albopictus cells, failed (i) to interfere with the replication of standard Sindbis virus and (ii) to change the pattern of intracellular viral RNA synthesis from that produced by infection with standard Sindbis virus alone. We conclude that defective interfering particles of Sindbis virus generated in chicken or hamster cells are silent or inert in mosquito cells.
Viral DNA-synthesizing intermediate complex isolated during assembly of bacteriophage phi X174
Authors: Fujisawa H , Hayashi M
Published: January 2020

A DNA protein complex that is a precursor of mature phi X174 phage was isolated. The complex sedimented with an S value of 50 in a sucrose gradient and contained phage DNA consisting of a replicative form molecule with an extended tail of single-stranded viral DNA. The viral-strand DNA ranged from one to two genomes in length. Proteins coded on the phi X174 genome as well as the host genome were associated with the viral DNA in the 50S precursor complex. Our results indicated that both viral DNA synthesis and cleavage of the growing viral-strand DNA occurred in the 50S complex.
Replication of bacteriophage T4 DNA in vitro. I. Basic properties of the system
Authors: Imae Y , Okazaki R
Published: January 2020

A new in vitro system for T4 DNA replication was developed by concentrating cell lysates on cellophane disks. The time course of [3H]dTTP incorporation into DNA by the system was separated into two phases: one was a very rapid incorporation which was terminated within 2 min (phase I reaction), and the other was a slow but continuous incorporation thereafter (phase II reaction). More than half of the phase I reaction product was Escherichia coli DNA, but the phase II reaction was mostly T4 DNA. Phase II reaction required four deoxyribonucleoside triphosphates, ATP, Mg2+, and KCl. 5-Hydroxymethyldeoxycytidine triphosphate was essential for the reaction and not substitutable by dCTP. The presence of KCN or NaN3 in the reaction mixture did not interfere with [3H]dTTP incorporation, but the addition of deoxyribonuclease completely degraded the system. Alkaline sucrose sedimentation analysis of phage II reaction product revealed that phase II reaction proceeded by the discontinuous mode of DNA replication as in vivo. After T4 infection, the activity for phase II reaction appeared in parallel with the activity of T4 phage DNA replication in vivo.
Selective decrease in the rate of cleavage of an intracellular precursor to Rauscher leukemia virus p30 by treatment of infected cells with actinomycin D
Authors: Jamjoom G A , Naso R B , Arlinghaus R B
Published: January 2020

The cleavage of an intracellular 67,000- to 70,000-dalton precursor, termed Pr4 to Rauscher leukemia virus (RLV) p30 protein proceeded at a slower rate when virus-producing cells were treated with actinomycin D (AMD). Treatment with AMD also caused a slight accumulation of Pr4 in purified early virus particles produced by a cell line which usually produces virions that contain little Pr4. The cleavage of other intracellular viral precursor polypeptides was not affected by treatment with AMD. Treatment of infected cells with cycloheximide, on the other hand, allowed the cleavage of Pr4 to proceed at the usual rate for a short period of time before further cleavage was drastically slowed or prevented. The cleavage of several other viral precursor polypeptides was also inhibited by treatment with cycloheximide. Different lines of evidence suggest that the mechanism of action of AMD is not due to a possible indirect effect on protein synthesis. Thus, the rate of cleavage of Pr4 was not affected by the length of pretreatment with AMD between 1 to 8 h. In addition, the combined effect of AMD and cycloheximide, at their maximal inhibitory concentrations, was greater than the effect of either drug alone, indicating the involvement of two at least partially different mechanisms in the action of AMD and cycloheximide. Furthermore, AMD did not affect the pulse labeling of viral precursor polypeptides. These results suggest that the interaction with viral RNA, whose production is inhibited by AMD, accelerates the cleavage of Pr4 to p30 during virus assembly. A hypothetical model is presented to illustrate th possible advantages of having a step in virus assembly in which genomic RNA interacts with a precursor to capsid proteins before the cleavage of that precursor.
Physical and metabolic requirements for early interaction of poliovirus and human rhinovirus with HeLa cells
Authors: Lonberg-Holm K , Whiteley N M
Published: January 2020

Attachment, ""tight binding'' and eclipse of radioactive poliovirus 2 (P2) and human rhinovirus 2 (HRV 2) were investigated. The activation energy for attachment of both HRV2 and P2 was about 13 kcal/mol. HRV2 differed from P2 in two respects: the Arrhenius plot for attachment of HRV2 showed a break at 15 to 19 degrees C when the cells were first treated several hours at 0 degrees C, and attachment of HRV2 was inhibited by treatment of cells with metabolic poisons able to reduce cellular ATP by more than 90%. Tight binding was determined by isolation of a specific P2-membrane complex or by loss of EDTA dissociability of HRV2. Tight binding of both viruses was slowed by 0.01 M iodoacetamide but not by 0.02 M F-; F- plus 0.002 M CN- slowed tight binding of HRV2 but not of P2. Eclipse, the irreversible alteration of parental virions, was detected by isolation of cell-associated subviral particles or by loss of cell-associated infectious virus. Eclipse of both viruses is slowed by iodoacetamide or F-. It seems likely that the early steps of infection with picornaviruses may be sensitive to alterations in the cell membrane produced by metabolic inhibitors or by treatment at low temperature.
Adenovirus transcription. IV. Synthesis of viral-specific RNA in human cells infected with temperature-sensitive mutants of adenovirus 5
Authors: Berget S M , Flint S J , Williams J F , Sharp P A
Published: January 2020

Cytoplasmic RNA sequences produced in HeLa cells infected with the adeno-virus 5 temperature-sensitive mutants ts1, ts2, ts9, ts17, ts18, ts19, ts20, ts22, ts49, ts36, and ts125 were characterized by hybridization to DNA probes generated by strand separation of restriction endonuclease fragments of adenovirus 5 DNA. Two ""early'' mutants defective in DNA synthesis, ts125 and ts36, fail to make wild-type levels of all previously reported classes of late RNA at the nonpermissive temperature. At 40.5 degrees C, both ts125 and ts36 synthesize a wild-type complement of early cytoplasmic RNA 16 h after infection. Under these conditions, no ""late'' cytoplasmic RNA sequences were observed. Similarly, nuclear RNA present in these cells resembled early cytoplasmic RNA rather than late nuclear RNA. All the late adenovirus 5 temperature-sensitive mutants synthesized normal wild-type levels of late cytoplasmic RNA at the nonpermissive temperature, except ts2, which appears to overproduce certain cytoplasmic species.
Natural immunity in mice to structural polypeptides of endogenous type C RNA viruses
Authors: Stephenson J R , Peters R L , Hino S , Donahoe R M , Long L K , Aaronson S A , Kelloff G J
Published: January 2020

The immunological responses of inbred mice to structural components of one class of endogenous virus were investigated by means of radioimmunoassays utilizing highly purified viral proteins. Naturally occurring antiviral antibodies were demonstrated only in those strains possessing information for induction of a mouse cell-tropic endogenous virus. Moreover, these antibodies invariably appeared subsequent to the detection of spontaneous replication of this virus in the same animal. The immune responses elicited were much stronger against endogenous viral gp70 than p30, consistent with previous findings of tolerance in the mouse to the major structural antigen of its endogenous virus. However, the demonstration of an immune response to p30 under conditions of both natural and experimental immunization establishes that tolerance to this viral antigen can be overcome.
Evidence of ambiguous processing and selective degradation in the noncapsid proteins of rhinovirus 1A
Authors: McLean C , Matthews T J , Rueckert R R
Published: January 2020

Pulse-chase kinetics and extensive pactamycin mapping studies show that the translation of rhinovirus 1A proceeds in the order: initiate-P1-S-P2-terminate, where P1 is the precursor to the capsid proteins, S is a stable primary gene product, and P2 is the precursor to a family of noncapsid products. Initial examination of the molar stoichiometry of the families of rhinoviral proteins in infected cells suggested that both the P1 and P2 regions were translated more frequently than the S region. However, we show that this apparent asymmetry in translation is an artifact arising from two phenomena: (i) ambiguous cleavage sites which result in two alternative products from the S region, having apparent molecular weights of 47,000 and 38,000, and (ii) several fates for the P2 precursors, including degradation of 35 to 45% of the P2 family to small unidentifiable products. Another artifact, a time-dependent shift in the pactamycin mapping position of polypeptide r-39, was traced to a selective inhibition of the rate of cleavage of its precursor (peak 76). The processing rate of the capsid precursor (peak 92) was not retarded by pactamycin.
Bacteriophage G4 DNA synthesis in temperature-sensitive dna mutants of Escherichia coli
Authors: Derstine P L , Dumas L B , Miller C A
Published: January 2020

The synthesis of bacteriophage G4 DNA was examined in temperature-sensitive dna mutants under permissive and nonpermissive conditions. The infecting single-stranded G4 DNA was converted to the parental replicative form (RF) at the nonpermissive temperature in infected cells containing a temperature sensitive mutation in the dnaA, dnaB, dnaC, dnaE, or dnaG gene. The presence of 30 mug of chloramphenicol or 200 mug of rifampin per ml had no effect on parental RF synthesis in these mutants. Replication of G4 double-stranded RF DNA occurred at a normal rate in dnaAts cells at the nonpermissive temperature, but the rate was greatly reduced in cells containing a temperature-sensitive mutation in the dnaB, dnaC, dnaE, or dnaG gene. RF DNA replicated at normal rates in revertants of these dna temperature-sensitive host cells. The simplest interpretation of these observations is that none of the dna gene products tested is essential for the synthesis of the complementary DNA strand on the infecting single-stranded G4 DNA, whereas the dnaB, dnaC, dnaE, (DNA polymerase III), and dnaG gene products are all essential for replication of the double-stranded G4 RF DNA. The alternate possibility that one or more of the gene products are actually essential for G4 parental RF synthesis, even though this synthesis is not defective in the mutant hosts, is also discussed.
Nonpermissive infection of L cells by an avian reovirus: restricted transcription of the viral genome
Authors: Spandidos D A , Graham A F
Published: January 2020

Avian reovirus multiples in chicken embryo fibroblasts. Although the avian virus adsorbs to L cells and is uncoated therein, it does not multiply. In the nonpermissive infection of L cells with the avian reovirus only four of the genomic segments of the viral genome are transcribed, L1, M3, S3, and S4, and these are the same segments that have been designated previously as early functions in the permissive infection of L cells with type 3 reovirus. When L cells are co-infected with avian reovirus and type 3 virus all ten segments of the avian viral genome are transcribed, although there is no synthesis of avian viral double-stranded RNA. Type 3 reovirus multiplies almost normally in this mixed infection. The most likely explanation is that a cellular repressor blocks transcription of the six late segments of the avian viral genome and that this repressor is removed by the co-infection with type 3 virus. A second block prevents replication of the viral genome.
Efficient Filtration and Sizing of Viruses with Membrane Filters
Authors: Ver Binie A. , Melnick Joseph L. , Wallis Craig
Published: January 2020

Untreated membrane filters retain viruses by adsorption, as well as by physical restriction which occurs when the pore diameter of the filter is smaller than that of the virus particle. As originally recommended by Elford, membranes had to be pretreated with proteinaceous material to preclude virus adsorption. However, coating materials that prevent adsorption of certain viruses do not necessarily prevent adsorption of other viruses. In contrast to proteins, salts enhance virus adsorption. Viruses treated with sodium lauryl sulfate to reduce the surface tension, or purified viruses in distilled water, are not adsorbed to membranes. A procedure is recommended by which viruses may be passed through membranes with a porosity twice the diameter of the virus. Such filtrates, which contain 50 to 100% of the initial virus concentration, should be used for sizing viruses by subsequent filtration through smaller pores. The determination of virus size would then be based on the major population of particles in the virus suspension. In the past, as little as 0.1 to 0.001% of the initial virus population was the basis for size determination, because more than 99.9% of the virus was often lost by adsorption to membranes during the clarifying procedures.
Protein Synthesis Directed by an Arbovirus
Authors: Friedman Robert M.
Published: January 2020

In contrast to chick embryo fibroblast protein synthesis, the bulk of the protein synthesis directed by Semliki Forest virus is carried out on membranes. Under conditions where more than 95% of cell protein synthesis was inhibited, viral polysomes could be demonstrated. Viral protein appeared to be produced on polysomes associated with nascent ribonucleic acid strands still attached to the base-paired, double-stranded replicative form of the virus. Very rapid incorporation of virus protein into 140
S
virus core particles was also demonstrated.
Structural and Nonstructural Proteins of an Arbovirus
Authors: Friedman Robert M.
Published: January 2020

Purified Semliki Forest virus (SFV) contains three structural proteins while its core (nucleocapsid) contains two of these proteins. To identify all of the proteins synthesized under virus direction, cells were infected with SFV in the presence of actinomycin D and guanidine. Cell protein synthesis was markedly and irreversibly inhibited under these conditions; virus growth was reversibly inhibited by guanidine and began when the cells were washed to remove the guanidine. When cells were treated with guanidine for 4 hr after virus infection and then were washed, five major proteins were produced early in infection. Three of these proteins corresponded to virus structural proteins. None of these five proteins was a major protein of uninfected cells or of virus-infected cells which had been incubated with partially purified interferon before infection. Late in infection, three major proteins, the virus structural proteins, were produced.
Escherichia coli
K Bacteriophages I. Isolation and Introductory Characterization of Five
Escherichia coli
K Bacteriophages
Authors: Stirm Stephan
Published: January 2020

A set of five
Escherichia coli
K phages has been isolated. These phages are adsorbed to and lyse the capsular forms of the host bacteria, whereas their spontaneous, acapsular mutants are not affected. All host strains are heavily encapsulated test strains for
E. coli
K antigens of the thermostable A type and they readily segregate acapsular mutants. In four of the phage-host systems, all secondary growth obtained was found to be acapsular. When tested for host-range mutants on 38 strains of
E. coli
and
Klebsiella
, less than one mutant per 10
5
plaque-forming units was found. No cross-reacting neutralizing antibodies were obtained when rabbits were immunized with the K phages. The latent periods (between 16 and 30 min) and average burst sizes (between 145 and 580) were determined by one-step growth experiments.
Viral Events Necessary for the Induction of Interferon in Chick Embryo Cells
Authors: Lockart R. Z. , Bayliss N. Lynn , Toy S. T. , Yin Fay Hoh
Published: January 2020

Temperature-sensitive mutants of Sindbis virus were employed to investigate the nature of the viral event(s) which induces chick-embryo cells to produce interferon. Chick embryo cells induced by the parental heat-resistant strain of Sindbis virus produced essentially equal amounts of interferon at 29 and 42 C. An RNA
−
and three RNA
+
strains [temperature-sensitive mutants unable (RNA
−
) and able (RNA
+
) to make ribonucleic acid] produced interferon at 29 C but not at 42 C. It is concluded that viral RNA per se and the replication of viral RNA do not induce interferon production by chick embryo cells.
Cellular Origin of a Mouse Leukemia Viral Ribonucleic Acid
Authors: Wollmann R. L. , Kirsten W. H.
Published: January 2020

Mouse erythroblastosis virus, a member of the mouse leukemia virus group, was obtained from chronically infected C
3
H mouse embryo cells and purified on sucrose gradients. The ribonucleic acid (RNA) extracted from ribonuclease-treated virus consisted of a rapidly sedimenting (72
S
) species and a more slowly sedimenting component (4 to 30
S
). The 72
S
RNA did not contain base sequences homologous to deoxyribonucleic acid (DNA) from infected cells as determined by hybridization studies. In contrast, the slowly sedimenting RNA enclosed within the virus had base sequences homologous to DNA from infected and uninfected C
3
H mouse embryo cells.
Electron Microscopic Observations of Mouse Brain Infected with Bunyamwera Group Arboviruses
Authors: Murphy Frederick A. , Harrison Alyne K. , Tzianabos Theodore
Published: January 2020

Ultrathin sections of brain tissue from mice infected with three Bunyamwera group arboviruses, Bunyamwera, Tensaw, and Maguari, were examined by electron microscopy. In all three cases, virus was observed budding from membranes into intracytoplasmic cisternae. Mature virus was found accumulated within these distended cisternae and in extracellular spaces. The three viruses were morphologically indistinguishable; particles were round or oval, 98 nm in diameter, and had a closely adherent irregular envelope.
Effect of Prophage W on the Propagation of Bacteriophages T2 and T4
Authors: Pizer Lewis I. , Smith Helene S. , Miovic Margaret , Pylkas Laird
Published: January 2020

Studies have been undertaken to determine whether the temperate phage ω present in
Escherichia coli
strain W is responsible for the inability of this strain to act as a host for T2 and T4.
E. coli
WS, cured of phage ω, was sensitive to T2 and T4. Lysogenation of
E. coli
C and WS with phage ω resulted in loss of ability to plate T2 and T4. However,
E. coli
K-12 lysogens still served as hosts for the T -even phage. Two of three WS lysogens studied resembled strain W at the biochemical level. They converted about 30% of infecting T2 deoxyribonucleic acid (DNA) to acid-soluble fragments and limited macromolecular synthesis to a few minutes after infection. The third lysogen did not degrade phage DNA, and nucleic acid and protein synthesis continued for some time, although no phage production occurred. It is concluded that phage ω plays a role in the restriction of virulent phage but that it is not the only factor involved. Since acid solubilization was not observed in all cases of phage ω-mediated restriction of T -even phage, a hypothesis for the restriction has been proposed which is based on an alteration in the cell envelope after lysogenation with phage ω.