bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitation of bovine papilloma viral DNA in viral-induced tumors
Authors: Lancaster W D , Olson C , Meinke W
Published: January 2020

Bovine papilloma virus (BPV) DNA was labeled in vitro under conditions of repair synthesis and subsequently used as a "probe" in DNA-DNA reassociation studies to detect BPV-specific DNA sequences in a viral-induced calf meningioma and hamster fibroma. In vitro labeled BPV DNA had denaturation characteristics expected for duplex DNA and denatured DNA reassociated with apparent second-order kinetics. Analysis of in vitro labeled BPV DNA reassociation rates in the presence of excess tumor DNA revealed that the calf meningioma contained approximately 700 to 800 BPV genome equivalents per diploid cell whereas the hamster fibroma contained about 150 incomplete BPV genome equivalents per diploid cell. Thermal denaturation of in vitro labeled BPV DNA which reassociated in the presence of the two tumor DNA preparations indicated less than 1.5% base pair mismatching.
Comparison of biophysical and morphological properties of occluded and extracellular nonoccluded baculovirus from in vivo and in vitro host systems
Authors: Summers M D , Volkman L E
Published: January 2020

Electron microscopic examination and buoyant density profiles of nonoccluded Rachiplusia ou and Autographa californica nuclear polyhedrosis viruses purified from both infectious insect hemolymph and cell culture medium revealed that the viruses are enveloped, single nucleocapsids. The envelopes exhibited variation in the amount and degree of fit with regard to the nucleocapsids. This was determined by: (i) electron microscopic observations of virus budding from the surface of infected cells; (ii) electron microscopic observations of negatively stained preparations of pelleted, highly purified, nonoccluded enveloped particles; and (iii) the resolution and density distributions of nonoccluded virus in sucrose gradients after centrifugation to equilibrium; all were compared with virus extracted from polyhedra. Peplomers, ovserved on the surface of enveloped nucleocapsids of nonoccluded virus, are not associated with polyhedra-derived virus. Density gradient analysis indicated that virus from insect hemolymph and culture medium exhibited similar densities of approximately 1.17 to 1.18 g/ml. This is significantly different from the buoyant density of an alkali-liberated, enveloped single nucleocapsid (1.20 g/ml). Results of this study show that the nonoccluded forms of two nuclear polyhedrosis viruses from two different sources, hemolymph and cell culture, are similar with regard to several morphological and biophysical characteristics but are quite different from the alkali-liberated, polyhedra-derived form of the virus.
Multiple origins and circular structures in replicating T5 bacteriophage DNA
Authors: Bourguignon G J , Sweeney T K , Delius H
Published: January 2020

Replicating T5 phage DNA was gently isolated using NaI density gradient centrifugation and examined by electron microscopy. At the beginning of phage DNA synthesis, linear unit-length T5 DNA molecules containing from one to four replicating "eye-loops" were consistently observed. Replication in these molecules was found to proceed bidirectionally from multiple, internal origins. A primary origin of replication is located near the center of the T5 genome, which does not coincide with the location of any of the nicks (single-strand breaks) found in mature T5 DNA. The initiation of replication at the various origins within an individual molecule does not appear to follow any definite temporal sequence. At later times in the infection, we have observed a significant number of circular T5 DNA molecules-both replicating and nonreplicating-whose average circumference is approximately the length of mature T5 DNA minus the terminal redundancy. The replicating circular molecules appear to be either in a theta configuration, a sigma configuration with the tails all being less than the length of the circle, or a combination of theta and sigma forms.
Isolation and Properties of the Replicase of Encephalomyocarditis Virus
Authors: Traub A. , Diskin B. , Rosenberg H. , Kalmar E.
Published: January 2020

The RNA-dependent RNA polymerase (replicase) of encephalomyocarditis (EMC) virus was found to be closely associated with the smooth membranes of infected BHK-21 cells. An RNA-dependent EMC replicase was extracted from the membranes with 0.15% sodium dodecyl sulfate (SDS) and 1,1,2-trichlorotri-fluoroethane (Genetron 113) and further purified by high-salt dextran-polyethylene glycol phase separation, sievorptive chromatography, and glycerol gradient sedimentation. The enzyme does not manifest strict specificity toward EMC RNA template. It can use also Qβ RNA, rRNA of BHK cells, or poly(C). SDS-polyacrylamide gel electrophoresis of purified EMC replicase labeled with radioactive methionine revealed that, of all the stable EMC proteins, the enzyme contains predominantly the 56,000-dalton (E) polypeptide.
Inherited resistance to N- and B-tropic murine leukemia viruses in vitro: titration patterns in strains SIM and SIM.R congenic at the Fv-1 locus
Authors: Schuh V , Blackstein M E , Axelrad A A
Published: January 2020

We have investigated the titration patterns of murine leukemia viruses on mouse embryo cultures derived from a pair of congenic strains differing at the Fv-1 locus. XC plaque and infectious center assays carried out with N- and B-tropic viruses on both SIM (Fv-1nn) and SIM.R(Fv-1bb) host cells yielded results that were best approximated by Poisson one-hit curves. Titration curves of N-tropic virus by direct XC plaque assay were linear and parallel on the different hosts, with titers 1.8 to 2.7 log10 lower on SIM.R and on (SIM X SIM.R)F1 than on SIM cells; similar linear and parallel curves were found for B-tropic virus, with titers 1.4 to 2.0 log10 lower on SIM and (SIM XSIM-R)F1 than on SIM-R cells. In the infectious center assays, the proportion of infected cells was linearly related to multiplicity of infection on both permissive (N- on SIM and B- on SIM.R) restrictive (B- on SIM and N- on SIM.R) genotypes at multiplicities of infection below 0.5; the line relating the variables was about 1 log10 lower in the restrictive than in the permissive situations. At multiplicities of infection where the proportion of infected cells reached a plateau, differences between the results on permissive and restrictive genotypes were considerably reduced. This appeared to be due to the action of non-Fv-1 factors in permissive host. We conclude that the major action of the restrictive allele at the Fv-1 locus in this system is to reduce the probability of successful murine leukemia virus infection without a change in hitness.
Characterizatiion of rat genetic sequences of Kirsten sarcoma virus: distinct class of endogenous rat type C viral sequences
Authors: Scolnick E M , Goldberg R J , Williams D
Published: January 2020

The nucleic acid sequences found in DNA and RNA from rat cells which are homologous to Kirsten sarcoma virus have been characterized. The homologous sequences are present in multiple copies per diploid rat cellular genome in a variety of different rat cellular dna's. In certain cells that constitutively express only low levels of sequences homologous to Kirsten sarcoma virus, bromodeoxyuridine treatment leads to the expression of high levels of these sequences in RNA. Supernatants from cell lines producing the sequences homologous to Kirsten sarcoma virus contain high levels of these sequences which are purified to the same degree as the previously known rat type C viral nucleic acid sequences by type C particles being released from such cells. The results indicate that the sequences in rat cells homologous to Kisten sarcoma virus have three characteristics of known mammalian type C viruses, and suggest that at least part of Kirsten sarcoma virus rat-derived sequences represent a distinct class of endogenous rat type C virus that has no detectable homology to the other known class of endogenous rat type C virus.
Sialylatin of glycoproteins of murine mammary tumor virus, murine leukemia virus, and Mason-Pfizer monkey virus
Authors: Schloemer R H , Schlom J , Schochetman G , Kimball P , Wagner R R
Published: January 2020

Neuraminidase treatment of mouse mammary tumor virus, Rauscher murine leukemia virus, and Mason-Pfizer monkey virus resulted in loss of their capacity to inhibit hemagglutination of influenza virus. Hemagglutination-inhibition activity of these RNA tumor viruses could be restored by in vitro resialylation catalyzed by sialyl transferase. The major glycoprotein in the intact envelope of desialylated and, to some extent, native virions could be specificallly labeled in vitro with CMP-(14C) sialic acid. These studies further characterize the individual glycoproteins of mouse mammary tumor virus, Rauscher murine leukemia virus, and Mason-Pfizer monkey virus.
Bacteriophage and bacteriophage-like structures carried by Bacillus medusa and their effect on sporulation
Authors: Hendry G S , Gillespie J B , Fitz-James P C
Published: January 2020

Bacillus medusa was found to carry three phages or phagelike structures named phi med-1, phi med-2, and phi med-3. phi med-1 is a minute, 25-nm-diameter particle without a tail. It was extracted from the sporulation lysate of a phi med-2-minus strain of B. medusa and purified by differential centrifugation. The nucleic acid from this structure was shown to be orcinol positive, alkali sensitive, RNase sensitive, and DNase resistant. An RNase-resistant core of nucleic acid was not found, indicating that it was single-stranded RNA. A host strain has not yet been found for phi med-1. Phage phi med-3 was induced with mitomycin C or UV light and consisted of empty heads of 57 nm in diameter, whereas phi med-2 induced with mitomycin was a phage of 60-nm head diameter and 220-nm tail length. The sporulation sequence proceeded faster in those mutants lacking phi med-2, and when the phage was reintroduced to B. medusa the extended wild-type sporulation sequence was observed. B. thuringiensis var. schwetzova was sensitive to phi med-2 and yielded small turbid plaques. B. medusa produced small numbers of phi med-2 during growth. The other phage may be produced at the same time but were not detected. Phi med-1 was found in sporulating cells by electron microscopy techniques. Its release from these was demonstrated by both electron microscopy techniques and a radioactive assay. It appears to participate in the formation of a surface layer on the parasporal inclusion of B. medusa.
Replication of mycoplasmavirus MVL51. IV. Inhibition of viral synthesis by rifampin
Authors: Das J , Maniloff J
Published: January 2020

The effect of rifampin on the replication of MVL51, a bullet-shaped mycoplasmavirus with single-stranded circular DNA of molecular weight 2 X 10(6), has been examined in a rifampin-resistant host cell. Rifampin does not block the early steps in MVL51 infection but does decrease the total amount of parental viral DNA taken up. The single-stranded parental viral DNA that enters the cell is found in membrane-associated, double-stranded DNA replicative forms I and II. Rifampin had no significant effect on the synthesis of progeny viral DNA RFI and RFII early in infection and SSI (single-stranded progeny viral chromosomes) later in infection. The rifampin block in virus synthesis was found to be in the step converting SSI into assembled virions. Rifampin was shown to affect the synthesis of virus-specific RNA, Which suggests that viral transcription is necessary for virion assembly.
Amphotropic host range of naturally occuring wild mouse leukemia viruses
Authors: Rasheed S , Gardner M B , Chan E
Published: January 2020

Seven murine leukemia virus field isolates (uncloned) from wild mice (Musmusculus) of four widely separated areas in southern California show an unusually wide in vitro host range. They replicate well in human, feline, canine, guinea pig, rabbit, rat, and mouse cells, whereas bovine, hamster, and avian cells are resistant. Since this host range includes that of both mouse tropic (ecotropic) and xenotropic murine leukemia viruses, they are designated as "amphotropic". No purely xenotropic virus component is detectable in these field isolates. They may represent the "wild" or ancestral viruses from which the ecotropic and xenotrophic murine leukemia virus strains of laboratory mice have been derived.
SAMase gene of bacteriophage T3 is responsible for overcoming host restriction
Authors: Studier F W , Movva N R
Published: January 2020

Deletion and point mutants of T3 have been isolated and used to show that the early region of T3 DNA is organized in the same way as that of T7 DNA. Homologous early RNAs and proteins of the two phages have been identified by electrophoresis on polyacrylamide gels in the presence of sodium dodecyl sulfate. Both phages have five early mRNA's, numbered 0.3, 0.7, 1,1.1 and 1.3 from left to right, although no T3 protein that corresponds to the 1.1 protein of T7 has yet been identified. In general, corresponding early RNAs and proteins of the two phages migrate differently on gels, indicating that they differ in molecular weight and/or conformation. In both T7 and T3, gene 0.3 is responsible for overcoming the DNA restriction system of the host, gene 0.7 specifies a protein kinase, gene 1 specifies a phage-specific RNA polymerase, and gene 1.3 specifies a polynucleotide ligase. The 0.3 protein of T3 is responsible for the S-adenosylmethionine cleaving activity (SAMase) induced after T3 (but not T7) infection. However, cleaving of S-adenosylmethionine does not appear to be the primary mechanism by which T3 overcomes host restriction, since at least one mutant of T3 has lost the SAMase activity without losing the ability to overcome host restriction.
Structure of Herpesvirus saimiri genomes: arrangement of heavy and light sequences in the M genome
Authors: Bornkamm G W , Delius H , Fleckenstein B , Werner F J , Mulder C
Published: January 2020

Herpesvirus saimiri contains two species of DNA molecules. (i) The M genome is composed of 70% light (L) DNA (36% cytosine plus guanine; density in CsCl, 1.695 g/ml), which consists of unique sequences, and 30% heavy (H) DNA (71% cytosine plus guanine; density, 1.729 g/ml). (ii) The H genome contains heavy sequences exclusively. H sequences in M and H genomes cross-hybridize completely and are cleaved identically by restriction endonuclease R-Sma I into four classes of fragments with molecular weights of about 360,000, 300,000, 130,000 and 40,000, respectively. H sequences are chains of identical repeat units in tandem arrangement. The molecular weight of each repeat unit is about 830,000. L sequences have no cleavage site for endo R-Sma I H sequences are terminally arranged at both ends of the M genome, as seen by electron microscopy after partial denaturation. The length of the individual heavy ends varies between 21 mum and less than 1 mum, whereas the light region is uniform in size (35.3+/-0.35 mum). As a rule, molecules with a long heavy end at one side have a short heavy end at the other side, thus giving rise to a limited size heterogeneity. Orientation of M DNA molecules by the denaturation map of the light region shows that the longer heavy end may be located at the left or at the right side of the M genome.
Naturally occurring murine leukemia viruses in wild mice: characterization of a new "amphotropic" class
Authors: Hartley J W , Rowe W P
Published: January 2020

A new class of murine leukemia viruses, isolated from wild Mus musculus trapped in California, is described. These viruses, designated "amphotropic," replicate in mouse, rabbit, mink, human, guinea pig, and rat cells, but not in hamster, quail, or duck cells. They show N-tropism for mouse cells, and do not trigger the XC cell response. They are distinct by interference and virus neutralization testing from the previously recognized mouse-tropic and xenotropic MuLV classes. Mouse-tropic viruses occuring along with three of the four amphotropic isolates were found to be distinguishable by virus neutralization from other mouse-tropic murine leukemia virus strains of laboratory mouse origin.
Orientation of the tox gene in the prophage of corynebacteriophage beta
Authors: Laird W , Groman N
Published: January 2020

The orientation of the gene for diphtheria toxin, tox, in the prophage of converting corynebacteriophage beta has been determined. The orientation of tox in prophage and that reported simultaneously by Holmes (1976) for vegetative phage are compatible with the hypothesis that beta phage is inserted into the chromosome of its bacterial host by means of a mechanism similar to that described for lambda phage, and that the phage attachment site lies between the tox and imm genes. The position of three tox mutations that are phenotypically CRM- has also been determined. Relative to the tox-45 mutation, they are located more proximally to the end of the tox structural gene that corresponds to the amino terminal of diphtheria toxin.
Characterization of adenovirus type 2 transcriptional complexes isolated from infected HeLa cell nuclei
Authors: Wilhelm J , Brison O , Kedinger C , Chambon P
Published: January 2020

HeLa cell nuclei, isolated 17 h after infection with human adenovirus type 2 (Ad2), were treated with 200 mM ammonium sulfate. The extract (S200 fraction) contained 50 to 70% of the nonintegrated Ad2 DNA, which was in the form of nucleoprotein complexes. These complexes contained native, intact Ad2 DNA (with the exception of replicative intermediates) and could be partially purified and resolved by velocity gradient centrifugation. Using high-salt (200 mM ammonium sulfate) incubation conditions, more than 95% of the nuclear RNA polymerase activity belonged to class B. About 45% of the class B enzyme molecules bound to DNA in the nuclei (those "engaged" in RNA synthesis) were released from the nuclei in the form of Ad2 transcriptional complexes by treatment with 200 mM ammonium sulfate. At least 90% of the RNA synthesized in high salt in the nuclei or in the S200 fraction was Ad2 specific, and essentially all of this RNA was complementary to the l strand of Ad2 DNA. These findings are compatible with what is known about Ad2-specific RNA synthesis in vivo. The analysis of the RNA synthesized from partially purified transcriptional complexes supports the contention that its transcription is almost entirely asymmetric, and that the asymmetry observed in vivo is not a consequence of the rapid degradation of h-strand transcripts. The RNA synthesized in vitro in the absence of detectable RNase activity sedimented with a maximum size of 35 to 40S. Less than 5% of the nuclear or the S200 fraction RNA polymerase activity was class C when assayed under non-reinitiating conditions. Although much of the RNA synthesized by the class C enzyme was Ad2 specific, 5.5S virus-associated RNA was not the predominant product. The isolation of Ad2 DNA transcriptional complexes provides an attractive system for further characterizing the Ad2 DNA template used for transcription and for studying the regulation of the expression of the Ad2 genome during the productive infection cycle.
Some biological and physical properties of molluscum contagiosum virus propagated in cell culture
Authors: Francis R D , Bradford H B
Published: January 2020

Molluscum contagiosum virus propagated in FL cells of human amnion origin has a one-step growth cycle time of 12 to 14 h. The appearance and exponential increase of intracellular virus preceded the release of extracellular virus by approximately 2 h. Demonstration of comparable titers of extracellular and intracellular virus at the end of the replication cycle indicated that a substantial amount of virus remained associated with cells exhibiting cytopathogenic changes. Mean buoyant density values of virus in sucrose ranged from 1.275 to 1.278 g/cm3, but in CsCl the virus banded at densities at 1.325 to 1.340 and 1.261 to 1.281 g/cm3. Although virus infectivity was not affected by high concentrations of CsCl, it was found by polyacrylamide gel electrophoresis that the salt removed several nonglycosylated polypeptides with estimated molecular weights of 15,000 to 60,000. This suggested that the high-density band (1.325 to 1.340) may reflect the loss of these structural components. The half-life of virus infectivity was approximately 26.5 h at 26 degrees C and 11.2 h at 37 degrees C. Although the virus was rapidly inactivated at 50 degrees C, it could be stabilized at this temperature by the presence of 1.0 M MgCl2. Virus did not agglutinate newborn chick, adult chicken, or type "0" human erythrocytes. Virus infectivity was found to be sensitive to acid pH but resistant to treatment with diethyl ether or chloroform. The replication of molluscum virus in FL cells was not inhibited by 5-iodo-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, or cytosine arabinonucleoside in noncytotoxic concentrations of 200 to 400 mug/ml, but greater than 99% reduction in the yield of herpes simplex virus or vaccinia virus in FL cells was obtained with 200 mug of these compounds per ml. Guanidinium chloride in concentrations of 100 to 200 mug/ml reduced molluscum virus yields by more than 99.9%.
Analysis of in vitro transcription products of intracellular vesicular stomatitis virus RNA polymerase
Authors: Galet H , Hallett D , Prevec L
Published: January 2020

The intracellular transcriptase complex of vesicular stomatitis virus-infected L cells synthesized RNA complementary to the entire infectious virus genome at either 37 degrees C or 28 degrees C in vitro. Not all sequences were present at the same frequency, however; copies of that segment of the genome common to the LT defective particles were present at 20 to 100 times higher frequently than copies of the genome segment common to the ST defective particle. The less frequent region was transcribed somewhat more effectively at 28 degrees C than at 37 degrees C. The results suggest that transcriptional regulation rather than selective degradation is responsible for the differential accumulation of RNA.
Genetic analysis of bacteriophage phi 29 of Bacillus subtilis: integration and mapping of reference mutants of two collections
Authors: Mellado R P , Moreno F , Viñuela E , Salas M , Reilly B E , Anderson D L
Published: January 2020

Reference mutants of Bacillus subtilis phage phi 29 of the Madrid and Minneapolis collections were employed to construct a genetic map. Suppressor-sensitive and temperature-sensitive mutants were assigned to 17 cistrons by quantitative complementation. Three-factor crosses were used to assign an unambiguous order for the 17 cistrons. Recombination frequencies determined by two-factor crosses were used to construct a linear genetic map of 24.4 recombination units. The genes were numbered sequentially from left to right (1 to 17) according to their relative map position.
Intermediates in adenovirus assembly
Authors: Edvardsson B , Everitt E , Jörnvall H , Prage L , Philipson L
Published: January 2020

Three intermediates in adenovirus assembly have been defined; nuclear intermediates, young virions, and mature virions. The nuclear intermediates are fragile and heterogenous in size (550S-670S) and withstand separation on ficoll gradients but fall apart upon CsCl gradient centrifugation unless prefixed with glutaraldehyde. They contain both capsid and core structures, and the core structures are preferentially released during purification in CsCl. The precursor polypeptides pVI and pVII are present in the intermediates without any corresponding mature polypeptide. The young virions (Ishibashi and Maizel, 1974) are stable and preferentially confined to the nuclei after cell fractionation. They contain both uncleaved precursor polypeptides and their cleavage products. The mature virions accumulate in the cytoplasm during cell fractionation and contain the final mature polypeptides. Pulse-chase labeling kinetics, focusing on the precursor polypeptides, suggest that these three classes participate in assembly of adenovirus. Tryptic peptide maps establish that polypeptide pVI is the precursor of polypeptide VI, but only a small fraction of polypeptide 26K can in vivo account for polypeptide VIII.
Conditional lethal mutants of adenovirus type 2-simian virus 40 hybrids. II. Ad2+ND1 host-range mutants that synthesize fragments of the Ad2+ND1 30K protein
Authors: Grodzicker T , Lewis J B , Anderson C W
Published: January 2020

Adenovirus type 2 (Ad2) grows 1,000 times less well in monkey cells than in human cells. This defect can be overcome, not only upon co-infection of cells with simian virus 40 (SV40), but also when the relevant part of the SV40 genome is integrated into the adenovirus genome to form an adenovirus-SV40 hybrid virus. We have used the nondefective Ad2-SV40 hybrid virus Ad2+ND1, which contains an insertion of 17% of the SV40 genome, to isolate host-range mutants which are defective in growth on monkey cells although they grow normally on human cells. Like Ad2, these mutants are defective in the synthesis of late proteins in monkey cells. A 30,000-molecular-weight protein (30K), unique to Ad2+ND1-infected cells, can be synthesized in vitro, using Ad2+ND1 mRNA that contains SV40 sequences. 30K is not seen in cells infected with those host-range mutants that are most defective in growth on monkey cells, and translation in vitro of SV40-specific mRNA from these cells produces new unique polypeptides, instead of 30K. Genetic and biochemical analyses indicate that these mutants carry point mutations rather than deletions.
Interaction of liposomes with subviral particles of poliovirus type 2 and rhinovirus type 2
Authors: Lonberg-Holm K , Gosser L B , Shimshick E J
Published: January 2020

Subviral particles ("A particles") were produced from rhinovirus type 2 by treatment with acid and from poliovirus type 2 by incubation at 37 degrees C in a low-ionic-strength buffer. A particles, but not virions, adsorbed to liposomes. It is proposed that these reactions may provide an in vitro model for two early steps of infection.
Lysine tRNA's associated with avian myeloblastosis virus 70S RNA
Authors: Carlson J V , Robey W G , Ortwerth B J
Published: January 2020

The lysine tRNA released from the 70S RNA of avian myeloblastosis virus was separated by reversed-phase chromatography. All of the AAG-coding lysine tRNA's were present in the 70S-associated fraction; however, the AAA-coding lysine tRNA could not be detected. Chromatography of the lysine tRNA released at various temperatures did not show any preferential release of one AAG-coding species over another.
Antigens and DNA of a chimpanzee agent related to Epstein-Barr virus
Authors: Gerber P , Pritchett R F , Kieff E D
Published: January 2020

Biological and biochemical studies of the herpesvirus of chimpanzees previously demonstrated to be antigenically related to human Epstein-Barr virus (EBV) indicated that the agent is similar to EBV in that: (i) leukocyte culture of chimpanzees whose sera contained antibody against EBV capsid antigen could yield long-term lymphoblastoid cell lines (Ch-LCL) with B-cell characteristics; (ii) the DNA of Ch-LCL contained sequences homologous to approximately 35 to 45% of human EBV; (iii) Ch-LCL contained an intranuclear antigen, Ch-NA, that could be identified with some chimpanzee or orangutan serum in anticomplimentary immunofluorescence assays; and (iv) treatment of Ch-LCL with iododeoxyuridine resulted in expression of new antigenic activity that reacted with EA+ but not EA- human sera. Two lines of evidence indicate that the chimpanzee agent, although related to human EBV, is a distinct agent: (i) Ch-NA was antigenically distinct from EBV-rebv infection although it cross-reacts of a limited extent with a minor component of EBNA; and (ii) Ch-LCL are missing 55 to 65% of the DNA sequences of human EBV.
Replication of T4 DNA in vitro. II. Assay system for and some properties of gene products required for T4 DNA replication
Authors: Imae Y , Shinozaki K , Okazaki R
Published: January 2020

[3H]dTTP was not incorporated into T4 DNA in the in vitro system for T4 DNA replication when the system was prepared from cells infected with T4 amber mutants defective in DNA replication. [3H]dTTP incorporation was resumed by adding the missing gene product to the defective system. DNA replication by the reconstituted system proceeded by the discontinuous mode of replication, as observed in the wild-type system. By using this in vitro complementation system, molecular weights of gene 41, 43, 44, 45, and 62 products in the active form were roughly estimated as 60,000, 130,000, 130,000, 60,000, and 130,000, respectively. Complex formation between the products of genes 44 and 62 was detected. Other strong interactions between the gene products tested were not detected by glycerol density gradient sedimentation. Interaction of gene products with denatured DNA was analyzed by using a DNA-agarose column, and the results showed that products of genes 32 and 43 had a strong affinity for DNA.
Suppression of glycoprotein formation of Semliki Forest, influenza, and avian sarcoma virus by tunicamycin
Authors: Schwarz R T , Rohrschneider J M , Schmidt M F
Published: January 2020

Tunicamycin, a new antibiotic, halts the formation of physical particles of Semliki forest and fowl plague virus, whereas avian oncornavirus particles which show a reduction in infectivity and do not contain detectable labeled glycoprotein are released in the presence of the drug. In Semliki forest virus-infected cells only the protein moieties of the glycoproteins could be labeled. In cells infected with fowl plague and avian sarcoma virus neither intact glycoproteins nor their protein moieties could be detected. By using a protease inhibitor (N-alpha-p-tosyl-L-lysin chloromethyl ketone, TLCK) it could be shown, however, that the carbohydrate-free hemagglutinin precursor of influenza virus is synthesized but is presumably degraded by intracellular proteases in the absence of TLCK as a consequence of the lack of carbohydrate.
Interactions of vesicular stomatitis virus with murine cell surface antigens
Authors: Hecht T T , Summers D F
Published: January 2020

The process of maturation of vesicular stomatitis virus (VSV) results in the loss of 70% of the H-2k antigenic activity from L-cell plasma membranes. This phenomenon is also demonstrated during VSV infection of cells of the H-2d haplotype. Using the method of inhibition of immune cytolysis, VSV-infected L5178Y tissue culture cells and VSV-infected METH A fibrosarcoma cells grown in vivo show a loss of H-2d activity of 73 and 76%, respectively. Using monospecific antisera, it is seen that VSV infection results in a significant loss of antigenic activity of the gene products of both the H-2D and H-2K regions in cells of the H-2d and H-2k haplotypes. In hybrid cells expressing H-2k as well as H-2b, VSV infection results in the decrease of both H-2 antigenic activities to the same extent. VSV purified from L cells shows considerable H-2k activity, but the reaction of this virus with anti-H-2k serum does not prevent a normal subsequent infection with this virus. VSV may associate with H-2 antigen in the culture medium, but the results of mixing VSV with uninfected H-2-containing homogenates suggest that this association occurs only when the host cell and the cell homogenate share the same H-2 haplotype. Velocity sedimentation of VSV, which would remove contaminating cellular membrane fragments, does not separate H-2 activity from VSV. H-2 activity is also stably associated with VSV throughout sequential sucrose gradient centrifugation steps. It is possible that H-2 antigen is a structural component of VSV grown in murine cells.
RNA-dependent DNA polymerase activity of RNA tumor virus. VI. Processive mode of action of avian myeloblastosis virus polymerase
Authors: Leis J P
Published: January 2020

Purified avian myeloblastosis virus (AMV) polymerase consisting of alpha,beta subunits has been shown to act processively in catalyzing DNA synthesis primed with 34S AMV RNA oligo(dT), poly(A)-poly(dT), and poly(I)-poly(dC). DNA transcripts prepared with 34S AMV RNA-oligo(dT)14 and AMV polymerase (alphabeta) have been shown to have a molecular weight of 1.05 X 10(6), or approximately one-third the size of the 34S RNA genome. Polymerase subunit alpha acts nonprocessively with the above templates.
Sequential Protein Synthesis Following Vaccinia Virus Infection
Authors: Moss B. , Salzman N. P.
Published: January 2020

Inhibition of HeLa cell protein synthesis and the sequential synthesis of viral proteins were followed by pulse-labeling infected cells with
14
C-phenylalanine. Proteins were resolved by polyacrylamide gel electrophoresis. The viral origin of native proteins was confirmed by immunodiffusion. The inhibition of host protein synthesis and the synthesis of early viral proteins occur 1 to 3 hr after infection. This early sequence of events also occurs in the presence of 5-fluorodeoxyuridine, an inhibitor of deoxyribonucleic acid synthesis. Other viral proteins are synthesized at a later time. Those proteins which are not made in the absence of viral deoxyribonucleic acid synthesis can be further subdivided into intermediate and late classes. The intermediate protein is synthesized before the late proteins but does not appear to be a precursor of them. Many more viral polypeptides were resolved by polyacrylamide gel electrophoresis after solubilization of the entire cytoplasmic fraction with sodium dodecyl sulfate. Virion and nonvirion proteins were identified. Kinetic experiments suggested that certain structural proteins as well as certain nonstructural proteins are made early, whereas others of both classes are made primarily at later times.
Replication of Western Equine Encephalomyelitis Virus II. Cytoplasmic Structure Involved in the Synthesis and Development of the Virions
Authors: Sreevalsan T. , Allen P. T.
Published: January 2020

Analysis of the cytoplasmic fraction of chick embryo cells during the exponential phase of Western equine encephalomyelitis (WEE) virus growth showed that the viral ribonucleic acid (RNA) labeled by a short pulse with
3
H-uridine was associated with a structure which sedimented in sucrose density gradients with a coefficient of 65
S
. The RNA extracted from this structure sedimented in sucrose density gradients at 26
S
. After a longer period of exposure to
3
H-uridine, the radio-active viral RNA was associated with a structure which sedimented in sucrose density gradients as would materials with coefficients of about 140
S
. The 140
S
structure contained viral RNA and viral protein. It was shown that the 140
S
structures are not virus-induced polysomes. The 140
S
structure contained predominantly the 40
S
type of viral RNA and some 26
S
type. Electrophoretic analysis of the disrupted virion revealed that at least two proteins (types I and II) were present in the purified virion. Only type II protein was present in the 140
S
structure. Unlike the virion, the 140
S
structure did not contain any lipid which could be detected by the incorporation of
14
C-choline. These data suggest that the 140
S
structure represents the internal nucleoprotein part of the virion. The rate of appearance of labeled virus lags behind that of the formation of the 140
S
structure in infected cells. Pulse-chase experiments with
3
H-leucine suggest that the 140
S
structure may represent a precursor to the virus particle. The results are discussed in terms of the maturation of WEE virus in the infected cells.
Electron Microscopy of Herpes Simplex Virus IV. Studies with Ferritin-conjugated Antibodies
Authors: Nii S. , Morgan C. , Rose H. M. , Hsu K. C.
Published: January 2020

Small aggregates of viral antigen were encountered in the nuclear matrix. The capsids did not tag with antibodies specific for the virus or for the host cell. This observation remains unexplained. Nuclear and cytoplasmic membranes, as well as the envelope of the virus, reacted with both types of antibodies and appear, therefore, to contain host cell and viral protein. Large amounts of viral antigen are synthesized within the cytoplasm. This antigen was either diffusely spread or localized at the surface of membranes. The surface of infected cells contains viral antigen, which accumulates as infection progresses. At circumscribed sites, the cell wall becomes altered antigenically and structurally so as to resemble the envelope of the virus. Hypotheses are presented regarding the manner in which cell fusion occurs.
Multiplication of Bacteriophage P1 Mutants in
Shigella dysenteriae
Strain Sh(P1)
Authors: Christensen J. R.
Published: January 2020

From bacteriophage P1, 10 mutants (P1cl) were isolated which are impaired in their ability to lysogenize
Shigella dysenteriae
Sh and which fail to make plaques when plated on Sh(P1). When Sh(P1) is infected with P1cl, a considerable proportion of the infected cells is converted into infectious centers, which eventually release P1cl but not P1. This phage release occurs over a period of several hours, during which a manyfold multiplication of infectious centers takes place. In the course of this multiplication, surviving bacteria, lysogenic for P1 only, are produced by segregation. At high multiplicity of infection, Sh(P1) are killed without producing any phage.
Host-controlled Restriction of T-even Bacteriophages: Relation of Endonuclease I and T-even-induced Nucleases to Restriction
Authors: Molholt Bruce , Fraser Dean
Published: January 2020

Restriction of nonglucosylated T2 phage (T
*
2) as a function of bacterial growth state was the same for endonuclease I-containing and endonuclease I-deficient strains of
Escherichia coli
B. Furthermore,
E. coli
strains with various levels of restriction for T2 had comparable endonuclease I activities. It was also found that a T4 mutant temperature-sensitive for gene 46 and 47 functions was fully restricted at 42 C. It therefore appears that neither endonuclease I nor the phage-induced nucleases whose activities are blocked by mutations in genes 46 and 47 catalyze the initial event in restriction of nonglucosylated T-even phages.
Adsorption of Bacteriophages to Adhesions Between Wall and Membrane of
Escherichia coli
Authors: Bayer M. E.
Published: January 2020

In plasmolyzed
Escherichia coli
, wall and membrane adhered to one another at 200 to 400 localized areas. This number of specialized wall areas per cell was of the same order of magnitude as the total number of bacteriophage receptors. When bacteriophages T1 to T7 were adsorbed to the bacteria, they were seen to attach almost exclusively to these areas. Comparisons of the number of adsorbed phage particles observed in ultrathin sections and the expected number of phages per cell were in agreement. These results suggest a sharing of receptive areas by the various phages. Adsorption to the wall-membrane associations would permit the virus to release its nucleic acid at an area closest to the cell's protoplasmic contents.
Rescue of Temperature-sensitive Poliovirus
Authors: Nichol F. Richard , Tershak Daniel R.
Published: January 2020

A temperature-sensitive strain of type 1 poliovirus, LSc, was functionally rescued when infected cells were incubated at 40 C in the presence of Mahoney, a temperature-resistant strain of type 1 poliovirus. The rescue value was 9% of the mutant yield obtained under permissive conditions. Rescued virus underwent replication, because the progeny of
32
P-labeled LSc were not radiosensitive. Serum inactivation studies with Mahoney specific antiserum indicated that a small amount of phenotypic mixing occurred among the rescued particles. The temperature-sensitive event occurred between 2 and 4 hr postinfection in the developmental cycle of LSc. Neither viral polymerase activity nor virus-induced ribonucleic acid could be demonstrated in infected cells between 2 and 4 hr after infection at 40 C with the temperature-sensitive mutant.
Role of Adenovirus Structural Proteins in the Cessation of Host-Cell Biosynthetic Functions
Authors: Levine A. J. , Ginsberg H. S.
Published: January 2020

Two of the adenovirus capsid proteins, the fiber and the hexon, complexed with either KB cell or type 5 adenovirus deoxyribonucleic acid (DNA). Maximal binding occurred at 0.01
m
NaCl; increasing the ionic strength of the reaction mixture to 0.2
m
NaCl resulted in a decrease in the association of either antigen to DNA. Variations of
p
H between 6.3 and 8.4 did not affect the binding of fiber antigen to DNA. Below
p
H 7.5, however, there was a small decrease in the ability of the hexon to bind nucleic acid. The association between the adenovirus structural proteins and DNA was reversible and was independent of whether the DNA was native or denatured. The fiber or hexon protein inhibited the DNA-dependent ribonucleic acid (RNA) polymerase and the DNA polymerase from KB cells. On a weight basis, the fiber protein inhibited enzymatic activity to a greater extent than the hexon. Increasing the template DNA concentration decreased this inhibition. The inhibition of the DNA-dependent RNA polymerase activity by either antigen could be reversed by increasing the ionic strength of the reaction mixture. After infection of KB cells with type 5 adenovirus, the levels of DNA and RNA polymerases remained unchanged for 15 to 20 hr. Thereafter, the specific activity of both enzymes decreased. By 30 hr postinfection, the polymerase activities were only about 30% of the enzyme activities in uninfected cells.
Integration and Induction of Phage P22 in a Recombination-deficient Mutant of
Salmonella typhimurium
Authors: Wing Jennifer P.
Published: January 2020

Phage P22 can integrate as prophage into a recombination-deficient (Rec
−
) strain of
Salmonella typhimurium
. At 37 C, the integration efficiency is only 10% that in Rec
+
infection, but at 25 C the efficiencies in Rec
−
and Rec
+
hosts are similar. Rec
−
lysogens cannot be induced by ultraviolet irradiation or by treatments with the chemical inducing agents streptonigrin or mitomycin C. Heat induction of Rec
−
cells lysogenic for a temperature-sensitive
c
2
mutant (
ts c
2
) is normal, showing that the Rec
−
cell has the machinery necessary for prophage excision. Ultraviolet irradiation of Rec
−
(
ts c
2
) lysogens prior to heat induction does not prevent the formation of infective centers after temperature shift. Thus, the noninducibility of Rec
−
lysogens is not due to destruction of the prophage as a result of ultraviolet irradiation. Deoxyribonucleic acid-ribonucleic acid (RNA) hybridization experiments demonstrate that no increase in phage-specific RNA synthesis occurs after ultraviolet irradiation of a Rec
−
(
c
+
) lysogen. The Rec
−
mutant appears to lack part of the mechanism required to destroy the phage repressor and allow the initiation of early phage functions such as messenger RNA synthesis. A similar conclusion was reached previously for an
Escherichia coli
Rec
−
strain.
Protective Effects of Specific Immunity to Viral Neuraminidase on Influenza Virus Infection of Mice
Authors: Schulman Jerome L. , Khakpour Manijeh , Kilbourne Edwin D.
Published: January 2020

Antibody specific for viral neuraminidase can be demonstrated in mice following (i) pulmonary infection with influenza virus, (ii) immunization with ultraviolet-in-activated influenza virus, (iii) immunization with isolated neuraminidase of influenza A
2
virus, and (iv) passive immunization with sera of rabbits immunized with isolated A
2
neuraminidase. Neuraminidase antibody produced by any of these methods exerts a profound inhibiting effect on virus replication in the lungs of mice challenged with strains of virus having homologous neuraminidase protein, even in the absence of hemagglutinating inhibiting antibody to the challenge virus, and results in markedly decreased pulmonary virus titers and diminished lung lesions. These observations suggest that antineuraminidase immunity may play a significant role in the protection against influenza virus challenge observed in mice after infection or artificial immunization.
Antiviral Activity of Polyacrylic and Polymethacrylic Acids
Authors: De Somer P. , De Clercq E. , Billiau A. , Schonne E. , Claesen M.
Published: January 2020

Polyacrylic acid (PAA) and polymethacrylic acid (PMAA) were investigated for their antiviral properties in tissue culture. Compared to other related polyanions, as dextran sulfate, polystyrene sulfonate, polyvinyl sulfate, and polyphloroglucinol phosphate, PAA and PMAA were found to be significantly more antivirally active and less cytotoxic. PMAA added 24 hr prior to virus inoculation inhibited viral growth most efficiently but it was still effective when added 3 hr after infection. Neither a direct irreversible action on the virus nor inhibition of virus penetration into the cell could explain the antiviral activity of PMAA. PMAA inhibited the adsorption of the virus to the host cell and suppressed the one-cycle viral synthesis in tissue cultures inoculated with infectious RNA.
Structure and Development of Viruses as Observed in the Electron Microscope
Authors: Morgan Councilman , Rose Harry M.
Published: January 2020

It is suggested that, after attachment of influenza virus to the cell, the viral coat disintegrates. With fusion of virus to the cytoplasmic membrane, the latter undergoes dissolution. Rupture of the viral core permits release of nucleoprotein directly into the cytoplasm. Stages in the process are illustrated.
Homologous interference of lymphocytic choriomeningitis virus: detection and measurement of interference focus-forming units
Authors: Popescu M , Schaefer H , Lehmann-Grube F
Published: January 2020

Lymphocytic choriomeninigitis (LCM) virus defective interfering (DI) particles form foci of protected cells in a monolayer under an agarose-containing overlay medium. Foci originate from one cell dually infected with at least 1 interference focus-forming unit and infectious virus. As a result, an interfering factor is produced and released which interacts with neighboring cells, thereby protecting them against cytopathic lysis by challenge virus. The property of individual LCM virus DI particles to induce countable foci has been made the basis of quantitative assay that is comparable in every respect to the plaque assay of infectious virus and is much more sensitive and probably more accurate than other procedures used to measure LCM virus DI particles. LCM virus was passaged, undiluted, 10 times in cell cultures. When yields were analyzed as to concentrations of PFU and interference focus-forming units, both entities were found to fluctuate with the pattern expected from theoretical considerations.
Interaction of elongation factor 1 with aminoacylated brome mosaic virus and tRNA's
Authors: Bastin M , Hall T C
Published: January 2020

Tyrosylated Brome mosaic virus RNA was found to interact with a binary complex of wheat germ, elongation factor 1 and [3H]GTP. Increasing amounts of the aminoacylated viral RNA proportionately reduced radioactivity bound to a nitrocellulose filter, as has previously been noted by others for the charged forms of tobacco mosaic virus, turnip yellow mosaic virus, and tRNA's. However, Sephadex chromatography of the products showed that instead of forming the ternary complex elongation factor-GTP-aminoacyl RNA, the viral RNA caused release of GTP from its complex with elongation factor. Acetylated tyrosyl Brome mosaic virus RNA did not react with the binary complex,and only a slight degree, if any, of stabilization of tyrosine bound to viral RNA was observed after interaction with elongation factor 1. Although such interactions are similar to the reaction of elongation factor with aminoacyl-tRNA , the release of GTP is different and accentuates the possible role for aminoacylation in transcription rather than in translation events.