bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical transformation of deoxythymidine kinase-deficient mouse cells with UV-irradiated equine herpesvirus type 1
Authors: Allen G P , McGowan J J , Gentry G A , Randall C C
Published: January 2020

A line of 3T3 mouse cells lacking deoxythymidine kinase (dTK-) was stably transformed to the dTK+ phenotype after exposure to UV-irradiated equine herpesvirus type 1 (EHV-1). Biochemical transformants were isolated in a system selective for the dTK+ phenotype (Eagle minimal essential medium containing 10(-4) M hypoxanthine, 6 X 10(-7) M aminopterin, and 2 X 10(-5) M deoxythymidine). Transformation was accompanied by the acquisition of a dTK activity with immunological, electrophoretic, and biochemical characteristics identical to those of the dTK induced by EHV-1 during productive infection. The transformed cells have been maintained in selective culture medium for more than 50 passages and have retained the capacity to express EHV-1--specific antigens. Spontaneous release of infectious virus has not been detected in the transformed lines, and the the cells were not oncogenic for athymic nude mice. In contrast to normal dTk+ 3T3 cells, EHV-1 transformants were unable to grow in the presence of arabinosylthymine, a drug selectively phosphorylated by herpesvirus-coded dTK's. These results indicate that a portion of the EHV-1 genome is able to persist in the transformed cells for many generations and be expressed as an enzymatically active viral gene product.
Correlated genetic and EcoRI cleavage map of Bacillus subtilis bacteriophage phi105 DNA
Authors: Scher B M , Law M F , Garro A J
Published: January 2020

The seven previously identified EcoRI cleavage fragments of phi 105 DNA were ordered with respect to their sites of origin on the phage genome by marker rescue. One fragment, H, did not carry any determinants essential for replication. This fragment was totally missing in a deletion mutant which exhibited a lysogenization-defective phenotype. There is a nonessential region on the phi 105 genome which begins in fragment B, spans fragment H, and ends in fragment F. The size of the nonessential region, as estimated by alterations observed in the fragmentation patterns of deletion mutant DNAs, is approximately 2.7 X 10(6) daltons. Two new EcoRI cleavage fragments with molecular weights of approximately 0.2 X 10(6) were detected by autoradiography of 32P-labeled DNA. These small fragments were not located on the cleavage map.
Restriction endonuclease mapping of bacteriophage phi105 and closely related temperate Bacillus subtilis bacteriophages rho10 and rho14
Authors: Perkins J B , Zarley C D , Dean D H
Published: January 2020

Cleavage maps of the three similar Bacillus subtilis temperate bacteriophages, phi105, rho10, and rho14, were constructed by partial digestion analysis utilizing the restriction endonuclease EcoRI. Comparison of the topography of these maps indicates that all phage DNAs posses cohesive ends and a number of EcoRI restriction sites; the fragments are conserved, and the estimated base substitution/nucleotide divergence between these phages is 0.03 to 0.07 based on conserved fragments or between 0.03 and 0.11 based on conserved cleavage sites. These lines of evidence indicate that phi105, rho10, and rho14 are closely related. Double-enzyme digestion analysis reveals that rho14 DNA has unique SalGI and BglII restriction sites and phi105 DNA has a unique SalGI restriction site, making these phages possible cloning vectors for B. subtilis.
Mechanism of transfection of chicken embryo fibroblasts by Rous sarcoma virus DNA
Authors: Cooper G M , Okenquist S
Published: January 2020

The mechanism of transfection by Rous sarcoma virus DNA was investigated by assaying DNA-mediated transformation under conditions which restricted secondary virus infection. Chicken embryo fibroblasts which were genetically resistant to virus infection as a result of the absence of receptors for virus penetration were also resistant to transformation by integrated or unintegrated Rous sarcoma virus DNA. In addition, DNA of replication-defective Bryan hightiter Rous sarcoma virus was noninfectious, and transformation by DNA of a temperature-sensitive DNA polymerase mutant was temperature sensitive. These results indicated that secondary virus infection was necessary for transformation by Rous sarcoma virus DNA. Since transformation was assayed by colony formation in soft agar, as well as by focus formation, the requirement for secondary virus infection was not an artifact of potential difficulty in detection of foci formed by division of single transformed cells. Therefore, it appeared that donor DNA did not stably transform recipient cells by direct integration. Instead, the results were consistent with the hypothesis that transfection of chicken embryo fibroblasts by Rous sarcoma virus DNA proceeded by transcription of donor DNA, formation of extracellular progeny virus, and secondary virus infection of sensitive cells.
Acquisition of oncogenicity by endogenous mouse type C viruses: effects of variations in env and gag genes
Authors: Devare S G , Rapp U R , Todaro G J , Stephenson J R
Published: January 2020

Several dual-tropic isolates derived from the thymuses of preleukemic or leukemic AKR mice and a more recrnt group of viruses generated by in vitro or in vivo passage of a poorly infectious endogenous virus of C3H mouse cells have been shown to be highly oncogenic. By analysis of the immunological properties of their gag gene-coded structural proteins, each of the AKR-derived isolates and two dual-tropic C3H-derived isolates were found to closely resemble AKR murine leukemia virus. In contrast, gag gene-coded proteins of two other leukemogenic isolates of C3H origin, including one ecotropic and one dual-tropic virus, were indistinguishable from those of Moloney murine leukemia virus. All of the oncogenic isolates, including those of AKR and C3H origin, were found to possess common envelope glycoprotein determinants of a unique class not shared by the nononcogenic ecotropic viruses from which they were derived. These findings support the possibility that oncogenic variants of endogenous ecotropic mouse type C viruses are derived by genetic recombination. This recombinational event appears to involve the acquisition, by different ecotropic viruses, of a common class of endogenous virus-coded envelope glycoprotein determinants which are presumably required, but not necessarily sufficient, for oncogenicity.
Mutants of Sindbis virus. III. Host polypeptides present in purified HR and ts103 virus particles
Authors: Strauss E G
Published: January 2020

The amounts of host-encoded protein present in purified Sindbis virions of both the HR strain and of a mutant (ts103) which makes multicored particles were examined. Cells were labeled with [35S]methionine before infection and with [3H]methionine postinfection. Virions were purified by velocity sedimentation and isopycnic banding, and their polypeptides were examined by polyacrylamide gels in a sodium dodecyl sulfate-containing discontinuous buffer system. Host prelabeled material was found principally in a small number of discrete polypeptides in HR virions, which contained as little as 0.2% host-encoded protein. Virus-sized particles of mutant ts103 contained significantly more host material, and multiploid particles from ts103 infection contained up to 12% host prelabeled protein.
Absence of circularly permuted and largely redundant sequences in the genome of visna virus
Authors: Vigne R , Filippi P , Brahic M , Tamalet J
Published: January 2020

A previous study of the infectivity of visna virus proviral DNA suggested that the genetic information of the virus is distributed over at least two of the RNA subunits. Because the genetic complexity of visna virus corresponds to the size of one subunit, this result may imply that sequence redundancies exist within each subunit. In the present article we have examined this question by constructing a map of the large RNase T1-resistant oligonucleotides of the viral genome. Our principal results are as follows: (i) all 36S RNA subunits have the same genetic content regardless of their polyadenylic acid [poly(A)] content; (ii) the poly(A) tract is present at the 3' end of the molecule; and (iii) the recoveries of 19 large RNase T1-resistant oligonucleotides from poly(A)-tagged RNA fragments of various sizes demonstrate that the oligonucleotides are organized in the same linear order within all subunits. Our results, therefore, exclude the existence of large sequence redundancies in the genome of visna virus.
Ends of the RNA within Sendai virus defective interfering nucleocapsids are not free
Authors: Lynch S , Kolakofsky D
Published: January 2020

Sendai virus defective interfering nucleocapsids, isolated from infected cell cytoplasm by equilibrium banding in CsCl gradients, contain only the viral N protein. Neither end of the genomic RNA within these nucleocapsids is accessible to RNase digestion.
Transcription of the transforming region of adenovirus type 5 in a rat cell line transformed by a small restriction fragment
Authors: Chinnadural G , Fujinaga K , Rho M H , van der Eb A J , Green M
Published: January 2020

The fraction of the adenovirus type 5 genome expressed as mRNA in a rat cell line, 5RK, transformed by the HsuI-G restriction fragment was analyzed by saturation hybridization using separated strands of 32P-labeled HindIII-G fragment. It was found that 45 to 50% of G fragment (about 8 X 10(5) daltons) is expressed as mRNA. The size of polyadenylic acid-terminated virus-specific cytoplasmic and nuclear RNA was determined by electrophoresis on polyacrylamide gels containing 98% formamide, followed by hybridization of gel slices with viral DNA. The major virus-specific RNA species present in the cytoplasm is about 14S, whereas the major virus-specific RNA present in the nucleus is 30 to 32S. The large size of nuclear virus-specific RNA suggests that host sequences are covalently linked to the viral transcript.
Genomic stability of gibbon oncornavirus
Authors: Sun L , Kawakami T G , Matoba S I
Published: January 2020

The 70S RNAs from several gibbon type C viruses were examined for sequence homology by molecular hybridization using complementary DNA probes. The sequence homology was found to vary with each virus isolate. The genome from one isolate was examined for genomic stability after the virus was experimentally passaged through three unrelated gibbons. The genomic homology remained unchanged after three passages, having greater than 93% homology based on complementary DNA-70S RNA hybridization and melting temperature analysis of the duplex. The genome from another isolate was similarly found to be unchanged after the virus was naturally transmitted in gibbons. The genomic variation found in the various isolates is not the consequence of recent horizontal transmission from a common virus.
DNA of Bacillus subtilis bacteriophage SPP1: physical mapping and localization of the origin of replication
Authors: McIntosh P K , Dunker R , Mulder C , Brown N C
Published: January 2020

The genome of Bacillus subtilis bacteriophage SPP1, a linear, 28.5-megadalton DNA duplex, was mapped by analysis with the restriction endonucleases endo R.Sal I, Sma I, Xba I, Bgl I, Bgl II, and EcoRI. The SPP1 genome, like that of the Salmonella typhimurium phage, P22, was found to be a terminally repetitious, circularly permuted molecule. 6-(p-Hydroxyphenylazo)uracil, a selective, reversible inhibitor of SPP1 DNA synthesis, was exploited to synchronize the initiation of genome replication and to selectively label the site of its initiation with radioactive thymidine. Restriction endonuclease analysis of the distribution of the label located the origin of replicative synthesis at an area approximately 0.2 genome length from one molecular terminus.
Restriction insensitivity in bacteriophage T5 I. Genetic characterization of mutants sensitive to EcoRI restriction
Authors: Davison J , Brunel F
Published: January 2020

Unmodified bacteriophage T5 is able to grow normally on bacterial hosts carrying three different Escherichia coli restriction systems, EcoK, EcoPI, and EcoRI. Under the same conditions, the plating efficiency of bacteriophage gamma is less than 10(-9). At least in the case of EcoRI, this lack of in vivo restriction is not due to lack of restriction sites on the T5 DNA molecule. These observations suggest that bacteriophage T5 specifies one or more restriction protection systems. Mutants (ris) of T5 have been isolated which confer sensitivity to EcoRI restriction but not to EcoK or EcoPI. The mutations are located in the pre-early region of the genetic map but are too far apart to be alleles of a single gene. Complementation studies show that the ris mutants can be helped to grow on the EcoRI-restricting host by coinfection with T5+. This result provides evidence for a restriction protection function but does not necessarily show that the ris mutants are defective in such a system.
Selective inhibition of protein synthesis in virus-infected mammalian cells
Authors: Contreras A , Carrasco L
Published: January 2020

A number of translation inhibitors were tested for their effects on both control and encephalomyocarditis virus-infected mouse 3T6 cells. The virus-infected cells were specifically inhibited by gougerotin, edeine, and blasticidin S, whereas these drugs failed to penetrate into uninfected cells. Inhibition of infected cells by gougerotin became apparent when the synthesis of viral proteins commenced, suggesting that the latter process is accompanied by a permeability change in the cells that allows uptake of the drug. This permeability change was not observed in cells treated with cycloheximide soon after viral infection, although treatment with actinomycin D did not prevent inhibition of gougerotin. It is possible, therefore, that a specific viral protein is involved in the permeability change of the plasma membrane. Moreover, gougerotin was unable to inhibit protein synthesis in the presence of zinc ions, thus preventing gougerotin from entering into the infected cell. Membrane leakiness was not restricted to the encephalomyocarditis virus-3T6 system; it was also observed in mengovirus-infected 3T6 cells, Semliki Forest virus-infected BHK cells, and simian virus 40-infected CVI1 cells at the time in which the synthesis of late proteins is maximal.
In vitro synthesis of infectious transforming DNA by the avian sarcoma virus reverse transcriptase
Authors: Clayman C H , Mosharrafa E , Faras A J
Published: January 2020

Infectious DNA molecules, capable of transforming chicken embryo fibroblasts, can be synthesized by the Rous sarcoma virus-associated reverse transcriptase in vitro. The optimal enzymatic conditions employed for infectious DNA synthesis also facilitate maximum synthesis of genome length DNA. Analysis of the DNA product synthesized by detergent-disrupted Rous sarcoma virus under these conditions indicates that DNA complementary to viral RNA (minus-strand DNA) is genome length in size, whereas DNA complementary to genome length minus-strand DNA (plus-strand DNA) appears as subgenomic-length molecules ranging between 300 and 3,500 nucleotides in length. These features of the DNA product synthesized by the Rous sarcoma virus reverse transcriptase in vitro are similar to those identified in the cytoplasm of cells shortly after infection and lend credence to studies of the mechanism of reverse transcription in vitro and their significance to proviral DNA synthesis in vivo.
Growth and Maturation of a Vesicular Stomatitis Virus Temperature-Sensitive Mutant and Its Central Nervous System Isolate
Authors: Hughes Joseph V. , Johnson Terry C. , Rabinowitz Stanley G. , Dal Canto Mauro C.
Published: January 2020

A temperature-sensitive (
ts
) mutant of vesicular stomatitis virus (VSV),
ts
G31, produces a prolonged central nervous system disease in mice with pathological features similar to those of slow viral diseases.
ts
G31 and the subsequent virus recovered from the central nervous system (
ts
G31BP) of mice infected with
ts
G31 were compared with the parental wild-type (WT) VSV for plaque morphology, growth kinetics, thermal sensitivity of the virions, and viral protein synthesis and maturation. Several properties of the central nervous system isolate distinguished this virus from the original
ts
G31 and the WT VSV. The WT VSV produced clear plaques with complete cell lysis, and the
ts
G31 produced diffuse plaques and incomplete cell lysis, whereas the
ts
G31BP had clear plaques similar to those of the WT VSV. Although plaque morphology suggested that
ts
G31BP virus was a revertant to the WT, growth kinetics in either BHK-21 or neuroblastoma (N-18) cells indicated that this virus was similar to
ts
G31, with a productive cycle at 31°C and no infectious virus at 39°C. At 37°C, however, the
ts
G31BP matured much slower than did the original
ts
G31 (and produced only 1% of the yield measured at 31°C). WT VSV produced similar quantities of infectious virions at 31, 37, and 39°C. The lack of infectious virions at 39°C for the
ts
mutants was presumably not due to a greater rate of inactivation at 39°C. Unlike WT VSV, which synthesized viral proteins equally well at all three temperatures,
ts
G31 had a reduced synthesis of all the structural proteins at 37 and 39°C, compared with that at 31°C; the formation of the M protein was most temperature sensitive. In addition, fractionation of the infected cells indicated that the incorporation of the M and N proteins into the cellular membranes was also disrupted at the higher, nonpermissive temperatures. Several characteristics of protein synthesis during
ts
G31BP infection at 39°C distinguished this virus from
ts
G31: (i) no mature viral proteins were detected at 39°C; (ii) several host proteins were [ill], suggesting that the virus was incapable of completely depressing host macromolecular synthesis; and (iii) a great proportion of the incorporated radioactivity was found in unusually high-molecular-weight proteins. In addition, at 37°C, the
ts
G31BP virus showed a decreased synthesis of viral proteins and reduced assembly of the viral structural proteins.
Selective Packaging of Host tRNA's by Murine Leukemia Virus Particles Does Not Require Genomic RNA
Authors: Levin Judith G. , Seidman J. G.
Published: January 2020

The 4S RNA contained in RNA tumor virus particles consists of a selected population of host tRNA's. However, the mechanism by which virions select host tRNA's has not been elucidated. We have considered a model which specifies that 35S genomic RNA determines which tRNA's are to be encapsidated as well as the relative amounts of these tRNA's within the virion. The model was tested by comparing the free 4S RNA composition of normal murine leukemia virus (MuLV) particles and noninfectious virions from actinomycin D (ActD)-treated cells, which are deficient in genomic RNA (ActD virions). Viral 4S RNA was analyzed by two-dimensional polyacrylamide gel electrophoresis. Surprisingly, the patterns obtained for control and ActD 4S RNA were identical to each other and were clearly distinct from the cell 4S RNA pattern. The viral patterns had three prominent areas of radioactivity. One of the spots was identified on the basis of its oligonucleotide fingerprint as tRNA
Pro
, the primer for MuLV RNA-directed DNA synthesis. These results were obtained with two different MuLV strains, AKR and Moloney, each grown in SC-1 cells. The demonstration that ActD virions contain primer tRNA and in general exhibit the characteristic MuLV tRNA pattern rather than the complete representation of cell 4S RNA leads to the conclusion that genomic RNA is not the major determinant in selective packaging of host tRNA's. A possible role for one or more viral proteins, including reverse transcriptase, is suggested.
Persistence of herpes simplex virus type 1 in rat neurotumor cells
Authors: Doller E , Aucker J , Weissbach A
Published: January 2020

Herpes simplex virus type 1 (HSV-1) infection of a rat central nervous system tumor cell line led to almost complete destruction of the cells. Cells that survived the infection could be isolated and shown to produce infectious HSV particles for variable lengths of time in culture ranging from 20 to 57 passages. Even though infectious virus production eventually ceased, the cell lines continued to produce herpes-specified proteins as measured by immunological techniques. These cells also showed herpesvirus-like structures in the electron microscope. The persistently infected cells that produced HSV antigens and bore HSV sequences were resistant to superinfection by HSV-1. The resistance was not due to failure of adsorption of the virus or to the production of interferon by the cells. The nature of the block in HSV replication in these neurotumor cells, which contain and partially express the HSV genome, is unknown, but may offer an interesting parallel to the known latency of HSV in neural tissues.
Effect of 5-methylcytidine on virus production in avian sarcoma virus-infected chicken embryo cells
Authors: Guntaka R V , Katz R A , Weiner A J , Widman M M
Published: January 2020

5-Methylcytidine (5mC) is a minor constituent of RNA in procaryotes as well as eucaryotes. The function of this modified nucleoside is not known. We studied the effect of this compound on virus production in avian sarcoma virus-infected chicken embryo fibroblasts. We found, surprisingly, that virus release into the medium was severely reduced in cultures treated with 5mC. In contrast to the effect of 5mC on virus release, intracellular levels of virus-specific RNA transcripts as well as the proteins were slightly elevated. Analysis of intracellular RNA transcripts on velocity gradients and virus-specific proteins in polyacrylamide gels did not reveal any qualitative differences in 5mC-treated cells compared to cytidine-treated cells. From these results we conclude that the effect of 5mC is probably at the level of virus maturation or packaging.
Serological definition of the lentivirus group of retroviruses
Authors: Stowring L , Haase A T , Charman H P
Published: January 2020

The major polypeptides of visna viruses and other lentiviruses have been isolated and shown to be closely related if not identical in radioimmunoassays. By this criterion the lentiviruses form a distinct group of retroviruses unrelated to spuma viruses, mammalian and avian retroviruses that cause tumors, and unclassified retroviruses of cattle and horses. Two sera obtained from goats immunized with Mason-Pfizer monkey virus or squirrel monkey virus reacted with visna p30. Additional data suggest that this reaction represents infection of goats with a lentivirus or a new retrovirus closely related to the lentiviruses.
Order of assembly of the lower collar and the tail proteins of Bacillus subtilis bacteriophage phi 29
Authors: Camacho A , Jiménez F , Viñuela E , Salas M
Published: January 2020

Extracts obtained after restrictive infection of Bacillus subtilis with mutants in cistron 11 of bacteriophage phi 29 are complemented in vitro by extract donors of the lower collar protein (p11). Purified 11- heads, containing the major capsid protein (p8), the fiber protein (p8.5), the upper collar protein (p10), and the virus DNA, can be also complemented in vitro to produce infective virus. This result suggests that 11- heads are intermediates in phage phi 29 morphogenesis. The order of assembly of the lower collar protein p11 and the tail protein p9 was determined in vitro in two complementation steps. The results obtained indicate that the lower collar protein is assembled before the tail protein.
Nuclear Accumulation of Influenza Viral RNA Transcripts and the Effects of Cycloheximide, Actinomycin D, and α-Amanitin
Authors: Mark George E. , Taylor J. M. , Broni B. , Krug R. M.
Published: January 2020

The use of virus-specific
32
P-labeled complementary DNA and
125
I-labeled virion RNA as hybridization probes has allowed us to quantitate the number of molecules of complementary RNA (cRNA) and progeny virion RNA in MDCK cells infected with influenza virus. We compared the distribution of cRNA between the nucleus and the cytoplasm in cycloheximide-treated cells to that found in untreated cells, beginning 1 h after infection. A greater percentage of the total cRNA was detected in the nucleus of the drug-treated cells at all times investigated. For the first 2 h after infection about 50% of the cRNA synthesized in the cycloheximide-treated cells was found in the nucleus. These nuclear cRNA molecules were characterized and shown to be polyadenylated transcripts of each of the genome virion RNA segments. Viral cRNA synthesis was not completely inhibited by the addition of actinomycin D at the beginning of infection, with or without the concomitant addition of cycloheximide. A large fraction (about 90%) of these cRNA sequences were detected in the nucleus. Characterization of these nuclear cRNA molecules showed that they contained polyadenylic acid and represented transcripts of both those segments coding for proteins synthesized predominantly early after infection (“early” proteins) and those virion RNA segments coding for “late” proteins. Also, in vitro translation of these cRNA molecules showed that they were functional virus mRNA's. In contrast to actinomycin D, α-amanitin completely inhibited cRNA synthesis when added at the beginning of infection, and addition of this drug after 1.5 h had no effect on further cRNA synthesis.
Monomer and multimer covalently closed circular forms of Rous sarcoma virus DNA
Authors: Goubin G , Hill M
Published: January 2020

Covalently closed circular molecules of viral DNA synthesized in virus-infected cells are composed mainly of monomers sedimenting at 22 to 27S in neutral sucrose gradients. These monomers are detected by annealing with complementary DNA or transfection assay. However, 11% of the infectious circles sediment faster than monomers. There is a peak at 32S which may correspond to dimer molecules. Traces of infectivity (about 3%) found between 32S and 65S suggest the presence of higher oligomers. In alkaline sucrose gradients, covalently closed monomers are found at 64 to 71S. Infectivity of these monomers is reduced by alkali treatment to less than one-tenth, and, perhaps for this reason, no infectious dimers or higher oligomers are observed. It has been shown that upon resedimentation the dimers of 95 can be separated from monomers and detected by hybridization.
Parental adenovirus type 2 genomes recovered early or late in infection possess terminal proteins
Authors: Straus S E , Sergeant A , Tigges M A , Raskas H J
Published: January 2020

At both early (3 h) and late (18 h) times after infection of KB cells with adenovirus 2, more than 90% of parental nuclear viral genomes exist as complexes which contain terminally linked proteins. Density shift experiments employing 5-bromo-2'-deoxyuridine indicate that these parental DNA molecules remain complexed with terminal proteins after DNA replication. The persistent linkage of proteins to the termini of intranuclear viral DNA suggests that these proteins have an essential role in adenovirus replication.
Characterization of Measles Virus-Specific Proteins Synthesized In Vivo and In Vitro from Acutely and Persistently Infected Cells
Authors: Rozenblatt Shmuel , Gorecki Marian , Shure Helen , Prives Carol L.
Published: January 2020

Measles virus protein synthesis has been analyzed in acutely and persistently infected cells. To assess the role of measles in subacute sclerosing panencephalitis (SSPE), measles viral proteins synthesized in vivo or in vitro were tested for reactivity with serum from a guinea pig(s) immunized with measles virus and sera from patients with SSPE. Guinea pig antimeasles virus serum immunoprecipitates the viral polypeptides of 78,000 molecular weight (glycosylated [G]), 70,000 molecular weight (phosphorylated [P]), 60,000 molecular weight (nucleocapsid [N]), and 35,000 molecular weight (matrix [M]) from cells acutely infected with measles virus as well as from chronically infected cells, but in the latter case, immunoprecipitated M protein has a reduced electrophoretic migration. Sera of SSPE patients immunoprecipitated all but the G protein in acutely infected cells and only the P and N proteins from chronically infected cells. In immunoprecipitates of viral polypeptides synthesized in a reticulocyte cell-free translation system, in response to mRNA from acutely or persistently infected cells, the 78,000-molecular-weight form of the G protein was not detected among the cell-free products of either mRNA. Guinea pig antimeasles virus serum immunoprecipitated P, N, and M polypeptides from the products of either form of mRNA, whereas SSPE serum immunoprecipitated the P and N polypeptides but not the M polypeptide. The differences in immunoreactivity of the antimeasles virus antiserum and the SSPE serum are discussed in terms of possible modifications of measles virus proteins in SSPE.
Membrane proteins specified by herpes simplex viruses. III. Role of glycoprotein VP7(B2) in virion infectivity
Authors: Sarmiento M , Haffey M , Spear P G
Published: January 2020

Experiments done with a temperature"sensitive mutant of herpes simplex virus type 1 (HSV-1) have revealed that one of the virisn glycoproteins, designated VP7(B2), is apparently not required for the production of enveloped virus particles, whereas it does play a critical role in virion infectivity. The mutant, designated HSV-1[HFEM]tsB5, fails to accumulate VP7(B2) at nonpermissive temperature and produces virions that lack detectable quantities of this glycoprotein and that have very low specific infectivity. The poor infectivity of the virions is most readily explained by failure of penetration into the host cell rather than by failure of adsorption to cells because it was shown that the VP7(B2)-deficient virions can bind to cells and that polyethylene glycol, an agent known to promote membrane fusion, can significantly enhance infectivity of the adsorbed virions.
Detection of the Viral Sarcoma Gene Product in Cells Infected with Various Strains of Avian Sarcoma Virus and of a Related Protein in Uninfected Chicken Cells
Authors: Brugge Joan S. , Collett Marc S. , Siddiqui Aleem , Marczynska Barbara , Deinhardt F. , Erikson R. L.
Published: January 2020

Genetic analyses have defined a single gene (
src
) as that portion of the avian sarcoma virus (ASV) genome which encodes the protein directly responsible for ASV-induced neoplastic transformation. We have recently identified the polypeptide product of the
src
gene of the Schmidt-Ruppin (SR) strain of ASV, a 60,000-dalton phosphoprotein designated pp60

src

, and have further determined that pp60

src

acts as a protein kinase. Essential to the identification and characterization of the pp60

src

protein of SR-ASV was the use of serum (TBR serum) from rabbits bearing SR-ASV-induced tumors. TBR serum was, however, strain specific, recognizing pp60

src

from SR-ASV-transformed cells only. We report here that sera from marmosets bearing tumors induced by the Bryan or SR strains of ASV (TBM sera) contain antibody which precipitates the transforming gene product from cells transformed by the SR, Bryan, Prague, or Bratislava strains of ASV. In contrast, rabbits bearing tumors induced by either the Bratislava or Bryan strains of ASV, or hamsters with SR-ASV-induced tumors did not produce antibody to pp60

src

from any strain of ASV. The 60,000-dalton polypeptides immunoprecipitated with TBM serum from cells transformed by each of the above virus strains are phosphoproteins. One-dimensional peptide mapping by limited proteolysis revealed that the pp60

src

proteins are structurally very similar, but not identical. Furthermore, all of the viral pp60

src

proteins have an associated phosphotransferase activity. In addition to detecting the viral
src
proteins, TBM serum was able to immunoprecipitate an antigenically related protein from normal uninfected avian cells.
Reevaluation of the proteins in rabies virus particles
Authors: Zaides V M , Krotova L I , Selimova L M , Selimov M A , Elbert L B , Zhdanov V M
Published: January 2020

Protein content and localization of individual proteins of rabies virus have been studied. Four major proteins (estimated molecular weights, about 65,000, 54,000, 37,000 and 21,000), one minor component (molecular weight, about 200,000), and one intermediate (as regards its molar concentration) component (molecular weight, about 43,000) were revealed in rabies virus particles. In subviral particles accumulating in virus-infected cells, the 200,000-, 54,000-, and 37,000-dalton components were revealed. Some properties of the subviral particles allow them to be considered as viral nucleocapsids and the proteins composing them as analogs of L, N, and NS proteins of other rhabdoviruses. Thus, the protein composition of the rabies virus strain studied does not differ from that of other rhabdoviruses.
Highly inducible cell lines derived from mice genetically transmitting the Moloney murine leukemia virus genome
Authors: Bacheler L , Jaenisch R , Fan H
Published: January 2020

Permanent, non-virus-producing cell lines have been established from a mouse embryo carrying an endogenous, genetically transmitted Moloney murine leukemia virus (M-MuLV) genome. These cells carry the M-MuLV genome, as demonstrated by hybridization of cellular DNA to M-MuLV complementary DNA, but do not express it at the levels of virus production, accumulation of intracellular viral p30, or M-MuLV-specific RNA. Treatment with bromodeoxyuridine (50 microgram/ml for 24 h) resulted in induction of XC-positive NB-tropic virus, although only a small fraction of the cells released virus (less than 0.1% after 48 h). Immunofluorescent staining and flow microfluorometry indicated that a wave of p30 accumulation occurs in the induced cells, with a maximum at 24 to 48 h after the addition of bromodeoxyuridine. Furthermore, most, if not all, cells were induced to produce p30 protein. Similar kinetics were found for the accumulation of M-MuLV-specific RNA in the cytoplasm of induced cells. This rapid induction of virus expression in a majority of cells was dependent on the presence of the M-MuLV genome and probably represents primarily the expression of this endogenous virus since induction was not observed in cells similarly derived from a sibling embryo lacking the M-MuLV genome.
DNA synthesis in Escherichia coli cells infected with gene H mutants of bacteriophage phi X174
Authors: Spindler K R , Hayashi M
Published: January 2020

Escherichia coli cells infected with gene H mutants of bacteriophage phi X174 produce two types of particles. The 110S particles contain single-stranded circular DNA; the 110S particles are not infectious, although their DNA is infectious for E. coli spheroplasts. The second type of particles, 70S particles, contain a fragment of single-stranded DNA ranging from 0.2 to 0.5 genome in length. This fragment DNA anneals only to restriction enzyme fragments of replicative-form DNA from the portion of the molecule corresponding to the origin and early region of phi X174 single-stranded synthesis, although full-round single-stranded DNA synthesis is occurring in the H mutant-infected cells. Different H mutant phages produce different proportions of 70S to 110S particles; those mutants producing the most 70S also exhibit the largest amount of degradation of intracellularly labeled DNA during infection. These results suggest that in H mutant-infected cells, full-length single-stranded DNA is synthesized; varying amounts of degradation of the single-stranded material occur, and the resulting fragment DNA is subsequently incorporated into 70S particles.
Simian Virus 40 Deoxyribonucleic Acid Replication
Authors: Kit Saul , Kurimura Takashi , de Torres Ramon A. , Dubbs Del R.
Published: January 2020

Infectious deoxyribonucleic acid (DNA) was extracted from green monkey kidney (CV-1) cultures at various times after the cultures were infected with simian virus 40 (SV40) at input multiplicities of 0.01 and 0.1 plaque-forming unit (PFU) per cell. A pronounced decrease in infectious DNA was observed from 3 to 16 hr after virus infection, suggesting that structurally altered intracellular forms may have been generated early in infection. Evidence is also presented that SV40 DNA synthesis requires concurrent protein synthesis. DNA replication was studied in the presence and absence of cycloheximide in: (i) SV40-infected and uninfected cultures of CV-1 cells; (ii) cultures synchronized with 1-β-
d
-arabinofuranosylcytosine (ara-C) for 24 to 30 hr prior to the addition of cycloheximide; and (iii) in heterokaryons of SV40-transformed hamster and susceptible monkey kidney cells. DNA synthesis was determined by pulse-labeling the cultures with
3
H-thymidine at various times from 24 to 46 hr after infection. In addition, the total infectious SV40 DNA was measured. Addition of cycloheximide, even after early proteins had been induced, grossly inhibited both SV40 and cellular DNA syntheses. The activities of thymidine kinase, DNA polymerase, deoxycytidylate deaminase, and thymidylate kinase were measured; these enzyme activities remained high for at least 9 hr in the presence of cycloheximide. SV40 DNA prelabeled with
3
H-thymidine before the addition of cycloheximide was also relatively stable during the time required for cycloheximide to inhibit further DNA replication.
Isolation of Naturally Occurring Viruses of the Murine Leukemia Virus Group in Tissue Culture
Authors: Hartley Janet W. , Rowe Wallace P. , Capps Worth I. , Huebner Robert J.
Published: January 2020

A tissue culture cell system for isolation and identification of members of the murine leukemia virus group (the complement fixation for murine leukemia test) was modified to permit the isolation of naturally occurring virus from leukemic and normal mice. The important factors for increasing the sensitivity of the test were the use of National Institutes of Health (NIH) strain Webster Swiss embryo cell cultures and the selection of rat-immune sera having complement-fixing antibodies to tissue culture antigens of both the Gross and FMR subgroups. In all, 163 strains of mouse leukemia virus, from 11 inbred mouse strains, have been isolated. Representative virus isolates were shown to possess the properties of the murine leukemia virus group; i.e., they were chloroform-sensitive, noncytopathic agents which replicated in mouse embryo tissue culture and produced group-reactive, complement-fixing antigen and budding C-type particles visible by electron microscopy. These viruses could serve as helpers in the rescue of Moloney sarcoma virus genome from non-producer hamster sarcoma cells, yielding pseudotypes. All of the 19 field isolates tested were neutralized by Gross passage A antiserum but not by potent antisera to the Moloney, Rauscher, and Friend strains. Virus was recovered regularly from embryos and from the plasma and spleen of adult mice of high leukemic strains. In low leukemic mouse strains, different patterns of virus detection were observed. In C3H/He mice, virus was occasionally present in embryos and was found in 40% of adult spleens. BALB/c mice were virus-negative as fetuses or weanlings, but spleens of more than half of the mice over 6 months of age yielded virus. NIH mice have never yielded virus. In reciprocal matings between AKR and BALB/c mice, virus recovery from embryos was maternally determined. The development of tissue culture isolation procedures made possible for the first time the application of classical infectious disease methods to the study of the natural history of murine leukemia virus infection.
Multiple Group-specific Antigen Components of Avian Tumor Viruses Detected with Chicken and Hamster Sera
Authors: Armstrong Donald
Published: January 2020

Multiple group-specific (gs) components of the avian leukosis-sarcoma viruses were detected by immunodiffusion (Ouchterlony) tests with sera from hamsters bearing tumors induced by sarcoma viruses and with sera from adult chickens immunized with avian sarcoma or leukosis viruses. Immune hamster sera detected up to four components, whereas chicken sera detected at least one. The hamster and chicken sera identified a similar antigen, as indicated by reactions of identity. Relatively few chicken sera containing neutralizing antibody to avian sarcoma or leukosis viruses reacted in immunodiffusion with the gs antigen. The gs components were released from the virion by various means of disruption, including freezing and thawing. Tests with tissues from normal chickens and from chickens with Marek's disease failed to demonstrate any reactions with hamster or chicken gs antiserum.
Length of Deoxyribonucleic Acid of PBSX-like Particles of
Bacillus subtilis
Induced by 4-Nitroquinoline-1-Oxide
Authors: Hirokawa Hideo , Kadlubar Fred
Published: January 2020

The formation of particles resembling PBSX phages was induced by 4-nitroquinoline-1-oxide in a Marburg strain of
Bacillus subtilis
. All particles were homogeneous in their morphology. Physical and biological analyses revealed that the deoxyribonucleic acid (DNA) carried by these particles are fragments of host-cell DNA. The contour length of the DNA is 4.25 μm, corresponding to a molecular weight of 8.1 × 10
6
daltons.
Defective Bacteriophage PBSH in
Bacillus subtilis
Authors: Haas Martin , Yoshikawa Hiroshi
Published: January 2020

PBSH, a defective phage of
Bacillus subtilis
strain 168, is described. Conditions are given for optimal induction of the prophage with mitomycin C. After a latent period of 90 min, cells were lysed and phage-like particles were released with a burst size of approximately 100 to 400 phage per bacterium. Since no known host supports phage replication after infection, burst size was determined by electron microscope count. Purification procedures and criteria for purity are described. The molecular weight of deoxyribonucleic acid (DNA) extracted from PBSH was estimated by length measurement and sedimentation. No circular DNA molecules were found by either technique. PBSH DNA molecules are linear, double-stranded, and of homogeneous molecular weight, about 12 × 10
6
daltons. There is no evidence for single-strand breaks. The majority of PBSH DNA molecules show a sedimentation behavior dependent on ionic strength. It is inferred that most of the DNA molecules are less hydrodynamically rigid than native DNA having a similar average base composition and molecular weight. Possible reasons for the sedimentation behavior are discussed.
Recombination Between Guanidine-resistant and Dextran Sulfate-resistant Mutants of Type 1 Poliovirus
Authors: Sergiescu Dina , Aubert-Combiescu Andrei , Crainic Radu
Published: January 2020

Mixed infection of monkey kidney cells with two mutants of the LSc2ab strain of poliovirus, one resistant to guanidine and the other resistant to both dextran sulfate and 2-(α-hydroxybenzyl)-benzimidazole (HBB), yielded progeny in which the number of
gua

r

dex

r

particles exceeded by a factor of 7 to 10 the expected number of similar particles occurring through spontaneous mutation; recombination would explain the fairly high excess of doubly mutant particles that was obtained. Scoring of HBB resistance in 50
gua

r

dex

r

clones suggested that, during recombination, resistance to dextran sulfate is not associated with HBB resistance.
Effect of Hydroxyurea on Replication of Bacteriophage T4 in
Escherichia coli
Authors: Warner H. R. , Hobbs M. D.
Published: January 2020

Hydroxyurea inhibited the replication of bacteriophage T4 in
Escherichia coli
B. The concentration of hydroxyurea required to inhibit net deoxyribonucleic acid (DNA) synthesis 50% was about 50-fold less than that required in uninfected cells. Even in the presence of high hydroxyurea concentrations, phage DNA was readily synthesized from the products of breakdown of the
E. coli
DNA, and viable phage were made. Deoxyribonucleotide, but not ribonucleotide, synthesis was strongly inhibited in the presence of hydroxyurea. The data indicate that hydroxyurea specifically inhibits de novo DNA synthesis in
E. coli
infected with bacteriophage T4 by inhibiting the ribonucleoside diphosphate reductase system, but does not affect DNA synthesis at subsequent steps.
Effect of Myxovirus Infection on Synthesis of Cellular Ribonucleic Acid
Authors: Ghendon Y. Z. , Ginsburg V. P. , Soloviev G. Y. , Babushkina Larisa
Published: January 2020

Ribonucleic acid (RNA) synthesis of chick embryo fibroblasts was inhibited by two members of the myxovirus group, Newcastle disease virus (NDV) and fowl plague virus. It was also found that cellular deoxyribonucleic acid-dependent RNA polymerase was inhibited by a cytoplasmic factor induced by NDV infection.
Synthesis of Saint Louis Encephalitis Virus Ribonucleic Acid in BHK-21/13 Cells
Authors: Trent Dennis W. , Swensen Connie C. , Qureshi Ateef A.
Published: January 2020

Infection of baby hamster kidney cells (BHK-21/13) with Saint Louis encephalitis (SLE) virus depressed the rate of protein and ribonucleic acid (RNA) synthesis until viral RNA synthesis began 6 hr postinfection (PI). Virus-directed RNA synthesis was subsequently inhibited until 12 hr PI when virion maturation began. The rate of protein synthesis reached a peak 6 hr PI and was subsequently depressed until just before the onset of virion maturation. Density gradient analysis of phenol-extracted RNA from actinomycin-treated infected cells indicated that, at 6 to 8 hr and again at 12 to 20 hr PI, three species of viral-specific RNA were synthesized. The most rapid sedimenting form (43
S
) was ribonuclease-sensitive and had a base composition similar to the RNA isolated from mature virions. The 20
S
RNA species was ribonuclease-resistant and had a sedimentation coefficient and base composition similar to the replicative form associated with other arbovirus infections. The 26
S
RNA was ribonuclease-resistant (0.2 μg/ml, 0.1
m
NaCl, 25 C, 30 min) and had a nucleotide base composition closer to the 20
S
form than to the values for 43
S
RNA. Five-minute pulse labeling of infected cultures during the period viral RNA synthesis was maximal resulted in labeling of only the 20S to 22S RNA fractions. With pulse-labeling periods of 10 min, both the 20
S
and 26
S
RNA species were radioactive. Periods of radioactive labeling of as long as 15 min were required before the 43
S
form was radioactively labeled. These results suggest that the 20
S
and 26
S
RNA may be intermediate forms in the synthesis of 43
S
viral RNA.
Differential Inhibition of Attachment and Eclipse Activities of HeLa Cells for Enteroviruses
Authors: Zajac Ihor , Crowell Richard L.
Published: January 2020

Receptor activities of HeLa cells were evaluated for ability to both attach and eclipse enteroviruses after exposure of cells to acid or heat. A modified procedure of acid (
p
H 1.5) elution of cell-associated virus, as compared with other procedures, provided a general method for the optimal recovery of receptor-bound enteroviruses. With this procedure, eclipse of virus operationally was considered to be that amount of virus infectivity which was determined initially to be cell-associated and which was not dissociable from the cells. HeLa cells killed by heating at 56 C for 30 min could not attach or eclipse poliovirus T1, but they attached and eclipsed coxsackieviruses B1 and B3, and they attached echovirus 6 but did not eclipse it. HeLa cells treated at
p
H 2.5 for 10 min at 2 C could not attach or eclipse poliovirus T1, but they attached coxsackieviruses B1 and B3 and echovirus 6, although these viruses were not eclipsed. These results showed that, within the operational definition of virus eclipse, the eclipse activity of HeLa cells for some viruses can be irreversibly inactivated without impairing the activity of the receptors for attaching these viruses. The data provided additional evidence that HeLa cells possess specific receptors for the different enteroviruses.