bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Nondefective Adenovirus-Simian Virus 40 Hybrids for Mapping the Simian Virus 40 Genome
Authors: Kelly Thomas J. , Lewis Andrew M.
Published: January 2020

A series of viable recombinants between adenovirus 2 (Ad2) and simian virus 40 (SV40) (nondefective Ad2-SV40 hybrids) have been isolated. The members of this series (designated Ad2
+
ND
1
through Ad2
+
ND
5
) differ from one another in the early SV40-specific antigens and the SV40-specific RNA species which they induce in infected cells. They also contain different amounts of SV40 DNA as shown by RNA-DNA hybridization techniques. We have examined the structure of the DNA molecules from these hybrids, using electron microscope heteroduplex mapping techniques. Each hybrid was found to contain a single segment of SV40 DNA of characteristic size covalently inserted at a unique location in the adenovirus 2 DNA molecule. The SV40 segments of the various hybrids formed an overlapping series with a common end point. When the results of the electron microscopic study were combined with data on antigen induction, it was found that a self-consistent map could be constructed which related specific regions of the SV40 genome to the induction of specific antigens. The order of these early SV40 antigen inducing regions in the SV40 DNA segments contained in the nondefective hybrids is: U antigen, tumor specific transplantation antigen, and T antigen with the U antigen region being nearest the common end point.
Unwinding of Parental Strands During Simian Virus 40 DNA Replication
Authors: Salzman N. P. , Sebring E. D. , Radonovich M.
Published: January 2020

Pools of young (less than 60% replicated) and mature (60-90% replicated) replicating molecules of simian virus 40 (SV40) DNA have been treated at pH 12.2 in order to dissociate growing chains from the parental strands. The molecules are neutralized so that the parental strands can reassociate and they have then been isolated. They are covalently closed structures which sediment rapidly in alkaline sucrose gradients; however, the sedimentation rates are less than the sedimentation rate of SV40 DNA I. Isopycnic banding in CsCl-ethidium bromide and sedimentation velocity studies in the presence of various amounts of ethidium bromide indicate that these structures contain negative superhelical turns and several-fold-higher superhelix densities than SV40 DNA I (the covalently closed DNA molecule). These structures are those that would be predicted if nicking, unwinding, and sealing of the parental strands occurred as replication proceeded. These experiments provide a direct demonstration that there is a progressive decrease in the topological winding number which accompanies SV40 DNA replication.
Immunoperoxidase Stain of Measles Antigen in Tissue Culture
Authors: Dubois-Dalcq M. , Barbosa L. H.
Published: January 2020

A specific electron microscopy staining technique for measles antigen has been developed by using Vero cells infected with a subacute sclerosing panencephalitis (SSPE) measles virus strain and fixed in glutaraldehyde or formaldehyde. Peroxidase-labeled antibody was prepared according to the method of Avrameas (4). Sera from SSPE patients with high measles antibody titer as well as normal human sera with and without measles antibody were used. With both fixatives, specific labeling was obtained on the surface of infected cells, on the budding site, and on complete viral particles. The cell membrane staining sometimes had a patchy distribution in that the reaction was most intense on the surface projections in front of each nucleocapsid. This suggests modification of the cell membrane in association with the nucleocapsids. In contrast, no label was detected on the membranes of the cells during the latent period from penetration through maturation of the virus. In formaldehyde-fixed cultures, cytoplasmic inclusions were stained, and this label was located on the “fuzzy” material around the nucleocapsids. The smooth type of nucleocapsids, mainly seen in the nucleus, were never labeled. These findings suggest that the antigenic nature of the “fuzzy” nucleocapsids in the cytoplasm may be different from that of the “smooth” nucleocapsids. The immunoperoxidase method gives good resolution of viral antigenic sites at high magnifications under electron microscopy and may be of value in studies on the immunopathogenesis of SSPE and other chronic viral infections.
Transduction of Gal
+
by Coliphage T1 III. Requirement for Transcription and Translation in Recipient Cells
Authors: Drexler Henry
Published: January 2020

A 10- to 15-min derepression of a λ prophage in a Gal
−
recipient during early infection with a transducing lysate of coliphage T1
am
will cause an increase in the efficiency of transduction of Gal
+
. An increase in the efficiency of transduction occurs when the donor is either nonlysogenic or lysogenic for λ; the increase is blocked by rifampin or chloramphenicol. With strain R901 it has been shown that efficient transduction can be blocked by treatment with rifampin after all chloramphenicol-sensitive steps have occurred.
Morphogenesis of Poliovirus II. Demonstration of a New Intermediate, the Proviron
Authors: Fernandez-Tomas Carlos B. , Baltimore David
Published: January 2020

Poliovirus-infected cells contain a previously unrecognized particle which appears to be an intermediate in virion synthesis and therefore has been named proviron. It sediments at about 125
S
, contains the three procapsid proteins, VP-0, VP-1, and VP-3, and has 35
S
viral RNA. It is disrupted both by sodium dodecyl sulfate and EDTA but the RNA resists digestion by ribonuclease. Pulsechase experiments and studies employing the virus-specific inhibitor, guanidine, all indicate that the proviron is formed by combination of newly made RNA with the procapsid. Cleavage of VP-0 to form VP-2 and VP-4 follows formation of the provirion and would be the final step in poliovirus morphogenesis.
Studies on the Mechanism of Replication of Adenovirus DNA II. The Nature of Single-Stranded DNA in Replicative Intermediates
Authors: Sussenbach J. S. , Ellens D. J. , Jansz H. S.
Published: January 2020

Replicative intermediates of adenovirus type 5 DNA contain large stretches of single-stranded DNA. We have shown that this single-stranded DNA is mainly of parental origin, whereas all new DNA synthesized during one round of replication has a double-stranded structure. Hybridization experiments of the single-stranded DNA with isolated complementary strands of adenovirus type 5 DNA showed that this DNA hybridized only with the viral L-strand (the strand with the lower equilibrium density in alkaline CsCl) indicating that it represents the viral H-strand. This observation implies that replication always starts from one and the same molecular end. Electron microscopy of partially denatured Y-shaped intermediates confirmed this and showed that replication started from the molecular right end (the end richest in A-T base pairs). In conclusion, we have shown that replication of adenovirus type 5 DNA starts at the molecular right end, displacing the parental H-strand.
Morphogenesis of poliovirus III. Formation of Provirion in Cell-Free Extracts
Authors: Fernandez-Tomas Carlos B. , Guttman Naomi , Baltimore David
Published: January 2020

Formation of an apparent virion precursor, the provirion, can be demonstrated in cytoplasmic extracts of poliovirus-infected HeLa cells.
Characterization of Virus-Specific RNAs from Subacute Sclerosing Panencephalitis Virus-Infected CV-1 Cells
Authors: Yeh Jen
Published: January 2020

CV-1 cells infected with subacute sclerosing panencephalitis (SSPE) virus incorporated uridine-
3
H
into at least four virus-specific RNA components in the presence of actinomycin D. The component sedimenting fastest had a sedimentation coefficient of 50
s
corresponding to a molecular weight of 6 × 10
6
. The other three RNA components have sedimentation constants of 35
s
, 22
s
, and 18
s
corresponding to molecular weights of 2.5 × 10
6
, 1.0 × 10
6
, and 0.75 × 10
6
, respectively. The base composition of the 50
s
RNA is distinct from that of cellular RNA and comparable with base compositions of viral RNAs of other paramyxoviruses. The base composition of the 18
s
RNA shows approximate complementarity with the 50
s
RNA. RNA-RNA annealing experiments using unlabeled 50
s
SSPE RNA with labeled 18
s
RNA from cells infected with SSPE virus or measles virus show 100% annealing with 18
s
SSPE RNA but only 60% annealing with 18
s
measles RNA. These experiments suggest some differences between the 18
s
RNAs of SSPE virus-infected cells and measles virus-infected cells.
Determination of the Molecular Weight of Animal RNA Viral Genomes by Nuclease Digestions I. Vesicular Stomatitis Virus and Its Defective T Particle
Authors: Repik Patricia , Bishop D. H. L.
Published: January 2020

A procedure has been developed for the determination of the weight of animal RNA virus genomes using controlled nuclease digestions and computation of the moles of oligonucleotides obtained from 1 mol of RNA. Using both pancreatic RNase and RNase T
1
to digest viral RNA labeled by
3
H-uridine,
3
H-cytidine, or
3
H-guanosine, the weight of the virion RNA of vesicular stomatitis virus (VSV) is estimated as 3.82 ± 0.14 × 10
6
whereas that of the VSV-defective T particle is estimated as 1.23 ± 0.04 × 10
6
.
Primary In Vivo Transcription of Vesicular Stomatitis Virus and Temperature-Sensitive Mutants of Five Vesicular Stomatitis Virus Complementation Groups
Authors: Flamand Anne , Bishop D. H. L.
Published: January 2020

The process of adsorption and RNA transcription by vesicular stomatitis virus (VSV) in cells has been followed by using highly labeled preparations of VSV virions. The initial transcription process (primary parental transcription) is rapid and takes about 4 min to develop complete transcripts of the input genome. The optimal cell temperature for in vivo transcription is between 36 and 39.5 C, although transcription can be detected at 18 C. No negative effect on primary parental transcription was obtained by the presence of actinomycin D, puromycin, or cycloheximide. Demonstrable primary transcription by selected temperature-sensitive mutants of all five complementation groups of VSV was obtained at either 31 and 34 C (permissive temperatures for virus production) or 39.5 C (nonpermissive temperature for virus development). VSV grown in hamster (BHK 21) or chicken embryo cells were more efficiently adsorbed and transcribed in BHK cells.
Host Effect on Arbovirus Replication: Appearance of Defective Interfering Particles in Murine Cells
Authors: Levin Judith G. , Ramseur Janet M. , Grimley Philip M.
Published: January 2020

Serial passage of Semliki Forest virus (SFV) in chicken embryo cells had little effect on SFV yield; however, high multiplicity infection of murine cells with one of the late passage pools (passage 9 SFV) resulted in a virus yield 10- to 20-fold lower than that obtained with earlier passage virus and 80-fold lower than the corresponding yield in chicken cells. This effect was accompanied by a striking decrease in the levels of 42
S
and 26
S
RNA and by increased proportions of a small single-stranded viral RNA (molecular weight, 9 × 10
5
) and of a low-molecular-weight replicative form. There was also a reduction in the number of specific membranous structures previously associated with the group A arbovirus replication complex. These results suggested that passage 9 SFV contained defective interfering particles which were detected more readily after one passage in a murine indicator host cell. Identical results were obtained with two different murine cell lines: one a leukemia virus-free clone of AKR cells and the other JLS-V9 cells chronically infected with Rauscher leukemia virus. Host production of RNA tumor virus particles apparently did not affect arbovirus replication.
Studies on the Biosynthesis of α-Putrescinylthymine in Bacteriophage φW-14-Infected
Pseudomonas acidovorans
Authors: Kelln Rod A. , Warren R. A. J.
Published: January 2020

The α-putrescinylthymine (putThy) in bacteriophage φW-14 DNA is synthesized at the mononucleotide level: it is labeled by uracil or deoxyuridine but not by thymidine, and it appears in the acid-soluble pool of infected cells before the onset of phage DNA synthesis. The methylene group at the C-5 position of the pyrimidine moiety of putThy is derived in vivo from a C
1
unit. Extracts of a phage infected thymidine auxotroph of the host,
Pseudomonas acidovorans
, apparently contain a phage-specific thymidylate synthetase and a phage-specific activity which forms 5-hydroxymethyl dUMP from
N
5
,
N
10
-methylene-tetrahydrofolate and dUMP.
Characterization of Influenza Virus Neuraminidases: Peptide Changes Associated with Antigenic Divergence Between Early and Late N2 Neuraminidases
Authors: Kendal Alan P. , Kiley Michael P.
Published: January 2020

Neuraminidases (EC 3.2.1.18) of 1957, 1960, and 1969 influenza virus strains were isolated after proteolytic digestion of viral hemagglutinin. Each neuraminidase was recovered with a final yield of about 15% and had similar specific activities. Immunization of rabbits with the neuraminidases elicited monospecific neuraminidase antibodies, with no antibodies to viral hemagglutinin. Further evidence of purity was the existence of only a single component, about 50,000 daltons in size, when reduced neuraminidase preparations were examined by sodium dodecyl sulfate acrylamide gel electrophoresis. However, storage of neuraminidase in solution resulted in the appearance of slightly smaller degradation products. Preparations of each neuraminidase were denatured under reducing conditions, and exposed sulfhydryl residues were blocked by reaction with
14
C-iodoacetamide. After tryptic digestion, peptide maps were prepared for the neuraminidases, and the
14
C-labeled cysteinyl peptides were then identified by autoradiography. About 20 peptides were present, in agreement with the number predicted from amino acid analysis for neuraminidase subunits of only one type. The 1957 and 1960 neuraminidases exhibited a small antigenic divergence from each other, and maps of their cysteinyl peptides appeared to be identical. The 1969 neuraminidase exhibited considerable antigenic divergence from the other two neuraminidases, and maps of 1969 neuraminidase peptides revealed two major and several minor differences from the other maps. Thus, antigenic divergence between the neuraminidases of Asian and Hong Kong influenza viruses is associated with a small number of changes in the primary structure of the neuraminidase subunit.
Outer Membrane of Avian Myeloblastosis Virus
Authors: Ishizaki Ryotaro , Luftig Ronald B. , Bolognesi Dani P.
Published: January 2020

Guinea pigs immunized intracerebrally with avian myeloblastosis virus (AMV) produced antiserum which reacted with intact virus particles in complement fixation. The antigen in question appeared to be located on the surface of the virion and could be distinguished from the type-specific virus envelope and the group-specific internal antigens of chicken leukosis-sarcoma viruses (ChiLSV). The material could be isolated by sequential treatments of AMV with bromelin, Tween 20, and freeze-thawing, and could be purified by differential centrifugation. Electron microscopy analysis indicated the presence of a component resembling the outer membrane of the particle. The antigenic determinant was designated virus membrane antigen (Vm). Further analyses revealed the presence of protein, lipid, and carbohydrate in a material having a molecular weight of about 6,000 as determined by sodium dodecyl sulfate gel electrophoresis. Serological studies suggested that the outer membranes of AMV and other ChiLSV are represented mainly by host cellular material.
Isolation of a Ribonucleoprotein Structure from Oncornaviruses
Authors: Fleissner Erwin , Tress Ellen
Published: January 2020

Detergent treatment releases from both avian and mammalian oncornaviruses a structure containing the viral RNA and a major arginine-rich protein, as well as reverse transcriptase activity.
Protein Kinase and Phosphoproteins of Vesicular Stomatitis Virus
Authors: Imblum Richard L. , Wagner Robert R.
Published: January 2020

Protein kinases of similar but not identical activity were found associated with vesicular stomatitis (VS) virions grown in mouse L cells, primary chicken embryo (CE) cells, and BHK-21 cells, as well as being present in VS virions grown in HeLa and
Aedes albopictus
cells. The virion kinase preferentially phosphorylated the nucleocapsid NS protein in vitro and to a lesser extent the envelope M protein. Other virion proteins were phosphorylated in vitro only after drastic detergent treatment. Partial evidence that the virion kinase is of cellular origin was obtained by finding reduced enzyme activity in virions released from cells pretreated with actinomycin D and cycloheximide. Selective detergent and detergent-salt fractionation of VS virions revealed that the kinase activity was present in the envelope but not the spikes. The virion kinase activity in a Triton-salt-solubilized envelope fraction could be separated from M and G proteins and partially purified by phosphocellulose column chromatography. Virions released from L, CE, and BHK-21 cells infected in the presence of [
32
P]orthophosphate were labeled almost exclusively in the NS protein. Both soluble and nucleocapsid-associated NS phosphoprotein were present in cytoplasmic extracts of VS viral-infected L cells. The origin and function of the NS phosphoprotein remain to be elucidated.
Virus Type-Specific Thymidine Kinase in Cells Biochemically Transformed by Herpes Simplex Virus Types 1 and 2
Authors: Davis D. B. , Munyon W. , Buchsbaum R. , Chawda R.
Published: January 2020

Transformation of mouse cells (Ltk
−
) and human cells (HeLa Bu) from a thymidine kinase (TK)-minus to a TK
+
phenotype (herpes simplex virus [HSV]-transformed cells) has been induced by infection with ultraviolet-irradiated HSV type 2 (HSV-2), as well as by HSV type 1 (HSV-1). Medium containing methotrexate, thymidine, adenine, guanosine, and glycine was used to select for cells able to utilize exogenous thymidine. We have determined the kinetics of thermal inactivation of TK from cells lytically infected with HSV-1 or HSV-2 and from HSV-1- and HSV-2-transformed cells. Three hours of incubation at 41 C produces a 20-fold decrease in the TK activity of cell extracts from HSV-2-transformed cells and Ltk
−
cells lytically infected with HSV-2. The same conditions produce only a twofold decrease in the TK activities from HSV-1-transformed cells and cells lytically infected with HSV-1. This finding supports the hypothesis that an HSV structural gene coding for TK has been incorporated in the HSV-transformed cells.
Structural Proteins of Mammalian Oncogenic RNA Viruses: Multiple Antigenic Determinants of the Major Internal Protein and Envelope Glycoprotein
Authors: Strand Mette , August J. T.
Published: January 2020

The antigenic determinants of two purified protein constituents of mammalian C-type RNA viruses, the major structural protein of about 30,000 daltons, and the membrane glycopeptides of about 70,000 daltons were examined by competition radioimmunoassay. By the appropriate choice of antiserum and competing proteins, it was possible to distinguish type-specific, group-specific, and interspecies determinants. Both of the viral constituents were found to contain each of these three classes of antigens. The results suggested that the majority of the determinants of the major structural protein were group specific, 5% to 30% were interspecies, and a small fraction were type specific. In the case of the envelope glycopeptides, the chief determinants were type and group specific, and a small fraction were interspecies.
Viruses of
Entamoeba histolytica
IV. Studies on the Nucleic Acids of the Filamentous and Polyhedral Viruses
Authors: Hruska Jerome F. , Mattern Carl F. T. , Diamond Louis S.
Published: January 2020

The nucleic acids of two amoebal viruses were studied by several independent methods. The filamentous virus, V
ABRM
, was shown to be inhibited by bromodeoxyuridine, iododeoxyuridine, and cytosine arabinoside. With acridine orange staining, V
ABRM
inclusions appeared greenish-yellow, indicating that these contained double-stranded nucleic acid. The polyhedral virus, V
301
, was also inhibited by bromodeoxyuridine, iododeoxyuridine, and cytosine arabinoside. In addition, nucleic acid hybridization showed that a new DNA species was synthesized in infected amoebal cultures. The intracellular localization of this new DNA was consistent with previous electron microscope studies of the cytoplasmic maturation of V
301
.
Virus-Induced Cytoplasmic Membrane Structures Associated with Semliki Forest Virus Infection Studied by the Freeze-Etching Method
Authors: Virtanen Ismo , Wartiovaara Jorma
Published: January 2020

Intracellular membrane structures associated with the Semliki Forest virus replication process were studied from freeze-etch replicas. Cleaved membrane structures inside the CPV I type vacuoles lacked the typical membrane particles present on most other fractured membranes. CPV II type vacuoles present in thin sections were obscured in the freeze-etch replicas by the cytoplasmic ground substance.
Suppression of a Mutation in Gene 3 of Bacteriophage T7 (T7 Endonuclease I) by Mutations in Phage and Host Polynucleotide Ligase
Authors: Sadowski Paul D.
Published: January 2020

Bacteriophage T7 bearing amber mutations in both gene 1.3 (T7 DNA ligase) and gene 3 (T7 endonuclease I) are viable when grown in suppressor-negative, ligase-negative hosts. This is evidenced by a high plating efficiency and a large burst size compared to the single mutants. These findings may be explained by a limited destruction of cellular DNA by the double mutant.
Relationship Between the RNA Polymerase Activities from Influenza Virions and Influenza Virus-Infected Cells
Authors: Horisberger M. , Guskey L. E.
Published: January 2020

Two RNA polymerase activities were characterized in the cytoplasm of influenza Ao/NWS infected cells. Their relationship to the virion-associated RNA polymerase was studied.
Viruses of
Entamoeba histolytica
V. Ultrastructure of the Polyhedral Virus V
301
Authors: Mattern Carl F. T. , Hruska Jerome F. , Diamond Louis S.
Published: January 2020

The polyhedral amoebal virus V
301
presents sectioned profiles consistent with its having icosahedral (532) symmetry. The DNA appears to be packed in an orderly, folded arrangement of lesser symmetry.
Replication of Reticuloendotheliosis Viruses in Cell Culture: Acute Infection
Authors: Temin Howard M. , Kassner Victoria K.
Published: January 2020

Replication of reticuloendotheliosis viruses (REV) in cultures of chicken and duck fibroblasts leads to some cell death soon after infection. This cell killing was used to develop a plaque assay for Trager duck spleen necrosis virus (TDSNV) on duck embryo fibroblasts. A normal replicative cell cycle was required for normal virus production and the development of cytopathic effects in chicken cells exposed to TDSNV. The latent period was about two days. Stationary chicken embryo fibroblasts could be infected by REV; DNA synthesis was required, but protein synthesis was not.
Detection of a Protein of Avian Leukoviruses in Uninfected Chick Cells by Radioimmunoassay
Authors: Chen J. H. , Hanafusa Hidesaburo
Published: January 2020

A radioimmunoassay (RIA) has been used to measure the quantity of protein P27 (mol wt 27,000; group specific-1 [gs-1]) of avian leukoviruses in different types of chicken embryos and tissues of adult chickens. The RIA used was 200- to 300-fold more sensitive than the complement fixation test and was able to detect as little as 0.3 ng of P27. Among six embryos tested, which are negative for gs antigen by the complement fixation test, P27 was undetectable in three embryos, but another three contained about 5 ng of P27 per mg of cell protein by RIA. The amount of P27 in gs antigen-positive cells ranged from 22 to 57 ng per mg of cell protein. P27 was found in liver, lung, ovary, feather pulp, and spleen from adult gs antigen-positive chickens. This protein was undetectable in various tissues from gs antigen-negative chickens.
Purification of Single- and Double-Length M13 Virions by Polyacrylamide Gel Electrophoresis
Authors: Beaudoin Jacques , Henry Timothy J. , Pratt David
Published: January 2020

Complete separation of single- and double-length M13 virions from each other and from still-longer phage particles was achieved by electrophoresis of phage stocks through 2.5% polyacrylamide gels.
Intracellular Virus-Specific Structures and RNAs in Oncornavirus-Producing Human Cells
Authors: Bukrinskaya A. G. , Miller G. G. , Lebedeva E. N. , Zhdanov V. M.
Published: January 2020

Two kinds of virus-specific structures were isolated from the cytoplasm of Detroit-6 and human amnion cells producing oncornavirus-like particles. These structures represented A particles with the diameter of 70 to 80 nm and aggregated strands of nucleocapsids with the diameter of 3 and 6 nm. The structures were separated from cellular contaminants by isopycnic banding in linear sucrose gradients and subsequently further purified by sedimentation in velocity sucrose gradients. Their sedimentation coefficient was 250 and 150
S
, respectively. Both structures contain 60, 45, and 35
S
RNA species, and 150
S
structures also contained 20
S
RNA. The 35 and 20
S
RNA from the 150
S
structure formed hybrids with DNA enzymatically synthesized on extracellular virions. The structures displayed endogeneous polymerase activity, DNA product of the reaction being predominantly associated with 60
S
RNA. No 70
S
RNA was found in the cell structures of various densities. Also, the virions purified from tissue culture fluid contained 70
S
RNA. These findings are consistent with those on extracellular maturation of oncornavirus RNA.
Vaccinia Virus Replication in Enucleate BSC-1 Cells: Particle Production and Synthesis of Viral DNA and Proteins
Authors: Pennington T. H. , Follett E. A. C.
Published: January 2020

The growth of vaccinia virus in monolayers of BSC-1 cells enucleated by centrifugation in the presence of cytochalasin B has been studied. No evidence for the production of infectious virus in these cells was obtained, and the production of virus particles was reduced to 8.3% compared with the yield from cytochalasin-treated, uncentrifuged cells. Virus DNA and early and late polypeptides were synthesized with normal timing in enucleate cells, but in reduced amounts; cleavage of structural polypeptide precursors P4a and Px also occurred in enucleate cells. Factories containing immature virus particles were demonstrated in enucleate cells by electron microscopy; these factories were reduced in number and size compared with those found in cytochalasin-treated, uncentrifuged cells.
Characteristics of φT, the Temperate Bacteriophage Carried by
Bacillus megaterium
899a
Authors: Hendry G. S. , Fitz-James P. C.
Published: January 2020

Phage T was the only phage observed in lysates of
Bacillus megaterium
899a induced with mitomycin C, 0.35 μg/ml. The phage adsorbed slowly to its host in nutrient agar, giving rise to plaques of varying sizes and turbidity. Only clear plaques were observed when the phage and host cells were preincubated in an adsorption buffer and plated under optimum conditions. Plaque turbidity was caused by either the addition of 0.5 × 10
−2
to 1.0 × 10
−2
M CaCl
2
to the phage assay medium, or by raising the incubation temperature to 34 C. Phage T purified on a CsCl gradient had a density of 1.48 g/ml in CsCl and the extracted phage DNA had a buoyant density in CsCl of 1.6975 g/ml, equivalent to 38.2% guanine plus cytosine. The phage was rapidly inactivated at 75 C and was unstable in the presence of chloroform at 4 C, but it was stable in buffer stored in ice. When stage I sporulating cells were induced with mitomycin C, phage were carried into spores which when germinated lyse with the release of φ T. The burst size on induction of early-log vegetative cells was 52, whereas the burst size of induced T
0
sporulating cells, diluted in fresh medium, was 47 for a sporulating strain and 140 for an asporogenous mutant. A typical phage T had a long, noncontracting tail 240 nm long, 9 to 11 nm wide, with a repeating disk unit along the tail, 4 nm in size center to center. The tail ended in a small disk (15 nm wide) which is presumably for attachment to the host. The hexagonal head measures 68 by 57 nm and is composed of donut-shaped units 9 nm in diameter.
Protein Kinase Associated with Sendai Virions
Authors: Roux Laurent , Kolakofsky Daniel
Published: January 2020

A protein kinase activity has been found associated with purified Sendai virions. Most of the virion proteins and exogenous protamine served as substrates for this enzyme.
Unusual Bacteriophages in
Salmonella newport
Authors: Ackermann Hans-W. , Petrow Sandra , Kasatiya Shanti S.
Published: January 2020

Six phages were isolated from sewage and from a lysogenic strain. Three of them, belonging to a new morphological group, had contractile tails and elongated heads with axial ratios of 2.4:1. Two phages, possessing short tails and very long heads with axial ratios of 3.5:1, were new isolates of an extremely rare group. Phages of both groups formed polyheads of various sizes and shapes. The last phage, 61 nm in diameter, seemed to have a tail-like appendage. All phages had double-stranded DNA, were active on enterobacteria only, and differed in their host range. The first five phages seemed to be
Salmonella
specific.
Intracellular Replication of Mycoplasmavirus MVL51
Authors: Liss Alan , Maniloff Jack
Published: January 2020

The intracellular replication of MVL51, a group L1 mycoplasmavirus, was investigated. The single-stranded parental DNA was found to enter the cell and become converted to double-stranded DNA. This replicated to yield additional double-stranded DNA molecules. The parental viral DNA was found to leave the replication complex and become associated with large molecular weight DNA not involved with viral replication. Progeny viral DNA formed from the double-stranded DNA and an intracellular accumulation of virus chromosome size DNA was observed. The interpretation of this data and a suggested model for the viral replication are discussed and compared to viral DNA replication models for other single-stranded DNA viruses.
Genetic Recombination in Bacteriophage φX174
Authors: Benbow Robert M. , Zuccarelli Anthony J. , Davis Gloria C. , Sinsheimer Robert L.
Published: January 2020

Genetic recombination in bacteriophage φX174 usually takes place early in the infection process and involves two parental replicative form (double-stranded) DNA molecules. The host
rec
A protein is required; none of the nine known φX174 cistron products is essential. The products of a single recombination event are nonreciprocal and asymmetric. Typically, only one of the parental genotypes and one recombinant genotype are recovered from a single cell. An alternative, less efficient recombination mechanism which requires an active φX174 cistron A protein is observed in the absence of the host
rec
A gene product.
Transcription and Replication of Vesicular Stomatitis Virus: Effects of Temperature-Sensitive Mutations in Complementation Group IV
Authors: Combard Arlette , Martinet Claire , Ane Christiane Printz , Friedman Annick , Printz Pierre
Published: January 2020

Temperature-sensitive (ts) mutants of vesicular stomatitis virus belonging to the RNA
−
complementation group IV were investigated under various conditions to study both their RNA and protein syntheses. In infected cells maintained at 39.2 C, viral RNA species were recovered only in the 13 to 15
S
region of the gradient in an amount depending on the ts mutant used. In the presence of cycloheximide at 39.2 C, the primary transcription was deficient, especially for 28
S
mRNA production. When mutant-infected cells were shifted to nonpermissive temperature, a shutoff of 28
S
mRNA synthesis occurred as a general feature. On the contrary under this condition, the two mutants chosen, ts IV100 and ts IV111, behaved very differently in their 13 to 15
S
and 38
S
RNA production. However, treatment with cycloheximide at the time of the transfer to 39.2 C resulted in a similar recovery of 13 to 15
S
RNA in both mutants, whereas the 28
S
remained very depressed. The viral proteins synthesized by cells infected with the same two mutants also showed a distinct pattern, especially regarding the N protein; a correlation between 38
S
RNA and protein N syntheses was tentatively drawn. The whole set of data suggested that the lesion in group IV mutants concerned a viral structural protein required for the process of in vivo transcription and which probably intervened in the replication mechanism.
Specific Serological Relationships Among Partially Purified DNA Polymerases of Avian Leukosis-Sarcoma Viruses, Reticuloendotheliosis Viruses, and Avian Cells
Authors: Mizutani Satoshi , Temin Howard M.
Published: January 2020

Specific serological relationships were found among the partially purified DNA polymerases of the two groups of avian viruses whose virions contain RNA and a DNA polymerase—the avian leukosis-sarcoma viruses and the reticuloendotheliosis viruses—and three avian species which are natural hosts for these viruses: chickens, turkeys, and Pekin ducks. No relationships were found to DNA polymerases of HeLa cells or
Escherichia coli.
These results are consistent with the hypothesis that RNA viruses with a DNA polymerase originated from normal cellular components.
Effect of Ionic Strength on the Binding of Sindbis Virus to Chick Cells
Authors: Pierce John S. , Strauss Ellen G. , Strauss James H.
Published: January 2020

Sindbis virus can adsorb to chicken embryo fibroblasts in two different ways. “Loosely” bound virus can be washed off the cell with buffers of ionic strength 0.2 or greater, whereas “tightly” bound virus remains attached under these conditions. When Sindbis virus is adsorbed to chick cells at 4 C from a buffer of ionic strength 0.17, 40 to 50% of the adsorbed virus is loosely bound, the remainder tightly bound. Infection of chick cells by Sindbis virus has only small effects on the total amount of virus that can be bound to the cells. However, the amount of Sindbis virus that can be tightly bound declines rapidly beginning at 2 to 3 h after infection. By 7 h after infection, the amount of virus that can be tightly bound is only 10 to 20% of the amount bound to uninfected cells. The adsorption (and penetration) of virus at 37 C is most efficient at an ionic strength of 0.15 to 0.17; at this ionic strength most of the adsorbed virus is tightly bound. At higher ionic strengths the virus adsorbs poorly. At lower ionic strengths most of the virus is loosely bound. A second enveloped virus, vesicular stomatitis virus, has been studied for the purposes of comparison; its adsorption behavior differs from that of Sindbis virus.
Separation of B and C Type Virions by Centrifugation in Gentle Density Gradients
Authors: Sarkar Nurul H. , Moore Dan H.
Published: January 2020

Murine type B particles were separated from type C (Rauscher leukemia virus) by means of gentle (low-increment rate) density gradients. The best separation was obtained when the density ranged from 1.13 to 1.20 g/cm
3
when sucrose was used and from 1.12 to 1.28 g/cm
3
with CsCl. The buoyant densities of the B and C particle bands in sucrose were 1.18 and 1.16 g/cm
3
, respectively. The CsCl gradient gave a better separation with the B particles banding at a density of 1.20 g/cm
3
and with the C particle density little different from its value in sucrose.
Excision of Thymine Dimers In Vitro by Extracts of Bacteriophage-Infected
Escherichia coli
Authors: Friedberg E. C. , Minton K. , Pawl G. , Verzola P.
Published: January 2020

Extracts of DNA polymerase I defective
Escherichia coli
infected with phage T4 contain an exonuclease activity that removes thymine dimers from UV-irradiated DNA previously nicked with T4 UV endonuclease. This activity is not expressed if cells are infected in the presence of chloramphenicol. The enzyme has a requirement for divalent cation and is not affected by caffeine, but excision is inhibited in the presence of proflavine. The enzyme is present in all phage T4 mutants thus far examined, including 25 UV-sensitive mutants isolated during the course of the experiments, all of which are defective in the
v
gene. A similar activity can be detected in cells infected with phages T2, T3, and T6, but not in cells infected with phage T7.
Scrapie and Transmissible Mink Encephalopathy: Search for Infectious Nucleic Acid
Authors: Marsh R. F. , Semancik J. S. , Medappa K. C. , Hanson R. P. , Rueckert R. R.
Published: January 2020

Brain preparations from animals with scrapie or transmissible mink encephalopathy were phenol extracted and examined for the presence of pathogenic nucleic acid. Animals inoculated with various extracts remained healthy, and analysis on 2.6 to 5% polyacrylamide gels failed to detect a difference in extractable RNA species between infected and normal mink brain.
Immunochemical Characterization of Two Major Polypeptides from Murine Mammary Tumor Virus
Authors: Parks Wade P. , Howk Richard S. , Scolnick Edward M. , Oroszlan Steve , Gilden Raymond V.
Published: January 2020

A major murine mammary tumor viral (MMTV) antigen, sl, originally described by Nowinski et al. (1967, 1968, 1971), has been purified from RIII mouse milk MMTV by sequential ion-exchange and gel chromatography. The purified protein with sl antigenic reactivity contains carbohydrate, and has an apparent minimal molecular weight of 52,000. It can be designated as gp52 (sl). Another major MMTV viral protein with a molecular weight of 27,000 has also been isolated, and antisera have been prepared against it. Both MMTV gp52 (sl) and p27 viral polypeptides have been iodinated with
125
I and used in immunoprecipitation and competition assays. The two MMTV proteins differ absolutely from each other and from major mouse type C viral polypeptides in molecular weight, immunological reactivity, and amino acid composition. Purified gp52 (sl) in radioimmunoprecipitation inhibition assays reacted in two distinct patterns. One pattern showed partial displacement of antibody which could be converted to the second, a complete displacement, by heating the antigen, presumably by exposing additional reactive determinants. Biologically, the patterns of major MMTV polypeptide expression in milk correlated with spontaneous mammary tumor incidence in different strains of mice, indicating that the sl antigen is group specific for MMTV or that several mouse strains contain the same virus type.
Virion-Bound Protein Kinase in Semliki Forest and Sindbis Viruses
Authors: Tan K. B. , Sokol F.
Published: January 2020

Semliki forest virus and Sindbis virus (Alphaviruses belonging to the togavirus group) grown in BHK-21 cells possessed very low levels of virion-associated protein kinase activity. For comparison, vesicular stomatitis virus, also grown in BHK-21 cells, contained a virion-bound protein kinase which had a specific activity 80 times greater than that of the Alphaviruses. The Alphavirus protein kinase was unmasked by the nonionic detergent Nonidet P-40 but was not activated by cyclic nucleotides. Phosvitin was the best exogenous phosphate acceptor for assaying the viral enzyme in vitro. Phosphoprotein phosphatase activity was also detected in the Alphaviruses. Both in vivo and in vitro, all of the viral structural polypeptides were phosphorylated, and the phosphorylated amino acids were found to be serine and threonine. The viral nucleocapsid protein was about four times more efficient as a phosphate acceptor than were the envelope proteins. From 33 to 50% of the total protein kinase was bound to the viral nucleocapsid, and the specific activity of this enzyme was 4 to 10 times greater than that associated with the viral envelope.
Endogenous C-Type Virus of a Mouse Cell Line and Its Defectiveness
Authors: Yoshikura H. , Hirokawa Yasuko
Published: January 2020

MLg cells originating from a newborn ddY mouse began to release C-type virus by treatment with 5-iodo-2′-deoxyuridine (5 μg/ml) for 48 h, or spontaneoulsy after prolonged cultivation. The data indicated the presence of three categories of the viruses spontaneously induced, i.e., virus equipped with the abilities of infecting and transforming the S+L- C182 cells, virus which can infect C182 cells but is unable to transform C182 cells, and virus which cannot infect nor transform the C182 cells, but is positive for the XC test. The type of the virus produced depended upon the cell clone. With the advance in the passage level, the cell population was dominated by the cells producing, uniquely, the last category of the virus.
Poly(A) Polymerase Activity in Reovirus
Authors: Stoltzfus C. M. , Morgan M. , Banerjee A. K. , Shatkin A. J.
Published: January 2020

An enzymatic activity which synthesized oligo(A) in vitro was found in highly purified reovirus. The poly(A) polymerase activity was dependent on Mn
2+
and utilized only ATP, whereas the virion-associated RNA polymerase required all four ribonucleoside triphosphates and Mg
2+
. Oligo(A) synthesis was demonstrated with complete virions and infectious subviral particles derived from virus by limited chymotrypsin digestion but not with cores, a product of extensive chymotrypsin digestion of virus. The enzymatic product and the oligo(A) from purified virions were isolated by binding to oligo(dT)-cellulose columns. Most of the in vitro product was similar in size and structure to the oligo(A) from purified virions by the criteria of gel electrophoresis, DEAE-cellulose chromatography, end-group analysis, and sensitivity to RNase. The evidence suggests that oligo(A) synthesis is mediated by the poly(A) polymerase during a late step in viral morphogenesis and may result from an alternative activity of the virion-associated transcriptase.
Bacteriophages of
Rhodopseudomonas spheroides
: Isolation and Characterization of a
Rhodopseudomonas spheroides
Bacteriophage
Authors: Abeliovich Aharon , Kaplan Samuel
Published: January 2020

A DNA-containing bacteriophage, designated RS1, infecting
Rhodopseudomonas spheroides
2.4.1, has been isolated from sewage. The buoyant density of RS1 in CsCl equilibrium centrifugation is 1.50 g/cm
3
, and the buoyant density of RS1 DNA is 1.706. The phage possesses a polyhedral head, approximately 65 nm in diameter, and a tail 60 nm long. When grown on aerobic cells, RS1 has a latent period of 120 min and an average burst size of 20. When grown on anaerobic cells, RS1 has a latent period of 150 min, and a burst size similar to that observed during aerobic infection. The adsorption rate constant of RS1 to aerobic cells is 1.2 × 10
−9
ml/min, and 0.58 × 10
−9
ml/min to anaerobic cells. Adsorption of RS1 to
R. spheroides
requires the presence of divalent cations.
Newcastle Disease Virus Infection of L Cells
Authors: Hecht Toby T. , Summers Donald F.
Published: January 2020

Newcastle disease virus (NDV) California strain reportedly grows poorly in L cells but replicates very well in chicken embryo cells. NDV-infected L cell cultures show a characteristic virus growth curve with respect to uridine incorporation, but plaque assays of the virus produced 24 h postinfection (PI) show no infectious particles when assayed on L cell monolayers and only a very low titer on chick cell monolayers. Plasma membranes isolated and purified from infected L cells 8 h PI contain all of the major virion proteins. In addition, NDV-infected L cells show a 50% loss of H-2 antigenic activity, a phenomenon previously observed in cells productively infected with vesicular stomatitis virus. These results suggest that at least part of the normal process of NDV maturation occurs in NDV-infected L cells. Sodium dodecyl sulfate-polyacrylamide gel patterns of supernatant virus purified from cells radiolabeled with amino acids from 3 to 24 h PI in the presence of actinomycin D show that all the major NDV structural proteins are present. Electron micrographs of NDV-infected L cells show extensive virus maturation at cell membranes. It can be concluded that infection of L cells with NDV results in a normal production of virus-specific RNA, synthesis of all the major structural proteins, association of the viral envelope proteins with the L cell plasma membrane, and the loss of cell surface H-2 antigenic activity. However, most of the virus particles produced are noninfectious.
Self-Annealing of Sendai Virus RNA
Authors: Kolakofsky Daniel , de la Tour Edward Boy , Bruschi Andrée
Published: January 2020

Both complementary strands are found in 50
S
Sendai virion RNA. 50
S
Sendai virion RNA has been shown to consist of unequal amounts of a single population of plus and minus strands by annealing studies.
Vaccinia Virus Polyriboadenylate Polymerase: Covalent Linkage of the Product with Polyribonucleotide and Polydeoxyribonucleotide Primers
Authors: Moss Bernard , Rosenblum Edith N.
Published: January 2020

A polyriboadenylate [poly(A)] polymerase, purified from vaccinia virus cores, was stimulated by polydeoxyriboadenylate: polydeoxyribothymidylate [poly(dA:dT)] and by polyribocytidylate [poly(C)] primers suggesting mechanisms of either transcription or terminal addition. Evidence for the latter was obtained by the demonstration of covalent linkages between the poly(A) products and both primers. In 99% dimethylsulfoxide-sucrose gradients, the sedimentation of poly(A) formed with poly(dA: dT) primer was reduced after DNase I treatment and the sedimentation of poly(A) formed with poly(C) primer was reduced by RNase A treatment, whereas the sedimentation of poly(A) formed without primer was not affected by either. Formation of a phosphodiester bond between primer and product was demonstrated by means of isotope transfer experiments.
32
P from α-[
32
P]ATP was transferred to 2′(3′)-CMP after alkaline or enzymatic hydrolysis of the poly(C)-primed polymerase reaction product. Transfer primarily or exclusively to 3′-dTMP was found after enzymatic hydrolysis of the poly(dA: dT)-primed polymerase reaction product. The elution pattern of the poly(A) polymerase from DNA-cellulose suggested that a single enzyme catalyzes the attachment of adenylate residues to both polyribonucleotide and polydeoxyribonucleotide primers; nevertheless the purest enzyme preparations contain two bands resolved by polyacrylamide gel electrophoresis in sodium dodecyl sulfate.
Mechanism of Poly (A) Synthesis by Vaccinia Virus
Authors: Sheldon Robert , Kates Joseph
Published: January 2020

Data are presented which indicate that vaccinia DNA does not contain poly(dT) sequences the size of poly(A) sequences (50 to 200 nucleotides in length) found in vaccinia RNA. A hybridization experiment and polyacrylamide gel electrophoresis and DEAE-Sephadex chromatography of pyrimidine tracts show that poly(dT) sequences can account for no more than 0.1% of vaccinia DNA. Ultraviolet irradiation (which causes thymine dimer formation) and phleomycin (which binds to thymidine) both inhibit RNA synthesis but not poly(A) synthesis by vaccinia cores. These data are consistent with a nontranscriptive mechanism for vaccinia poly(A) synthesis. Both trypsin and 50 C heat treatment inhibit RNA synthesis more than poly(A) synthesis by cores, suggesting that separate enzymes may be involved in these syntheses. When the rate of core RNA synthesis is reduced by lowering the UTP and GTP concentrations, the size of the poly(A) sequences increase. These and other data suggest that transcription is involved in the termination of poly(A) synthesis in cores. This might be due to the displacement of growing poly(A) chains by recently completed RNA 3′ termini which have not yet acquired poly(A) sequences.