bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Interferon Action: Inhibition of Viral Messenger Ribonucleic Acid Translation in L-Cell Extracts
Authors: Friedman R. M. , Metz D. H. , Esteban R. M. , Tovell D. R. , Ball L. A. , Kerr I. M.
Published: January 2020

Encephalomyocarditis (EMC) virus ribonucleic acid (RNA) stimulated the incorporation of
14
C-amino acids into polypeptides in cell-free systems using preincubated S10 extracts from L cells. Incorporation was linear for over 2 hr. Analysis of the tryptic peptides derived from the polypeptide products formed in response to EMC RNA showed them to be virus specific. The major product, a polypeptide of 140,000 in molecular weight, migrated on sodium dodecyl sulfate-polyacrylamide gels with one of the virus-specific polypeptides present in EMC-infected cells. A minor component of molecular weight about 230,000 may correspond to the product of complete translation of the EMC virus genome. Little or no effect of interferon or vaccinia virus infection was observed in the preincubated, cell-free system. The EMC RNA-stimulated incorporation of
14
C-amino acids into polypeptides was not inhibited in extracts derived from L cells early in virus infection, from interferon-treated cells, or from cells subjected to both treatments. Interferon treatment did appear to have a slight inhibitory effect on chain elongation in this system. However, treatment of cells with highly purified interferon before virus infection caused a decrease of about 80% in the capacity of non-preincubated cell extracts to translate added EMC RNA. This effect did not extend to the translation of polyuridylic acid and could be reversed by preincubation of the extracts at 37 C for 20 min. The inhibition of translation was manifest at interferon concentrations as low as 5IU/ml, and in this respect closely paralleled the inhibition of virus growth. Inactivation of the antiviral activity of the interferon by heating or digestion with trypsin also abolished the effect on cell-free protein synthesis. The EMC-specific polypeptides formed in reduced amounts in extracts of interferon-treated vaccinia-infected cells were smaller than those formed in extracts of untreated, vaccinia-infected cells. Thus, inhibition of initiation or elongation of polypeptides, or both, can be demonstrated in cell-free systems employing non-preincubated extracts from interferon-treated, virus-infected cells. These results indicate that antiviral activity of interferon is directed against the translation of viral messenger RNA.
Molecular Weights of Vesicular Stomatitis Virus and Its Defective Particles by Laser Light-Scattering Spectroscopy
Authors: Ware B. R. , Raj Tilak , Flygare W. H. , Lesnaw J. A. , Reichmann M. E.
Published: January 2020

Laser light-scattering spectroscopy has been used to determine the diffusion coefficients of vesicular stomatitis virus and three of its defective particles in order to calculate their molecular weights.
Measles Virus Ribonucleic Acid and Protein Synthesis: Effects of 6-Azauridine and Cycloheximide on Viral Replication
Authors: Portner Allen , Bussell Robert H.
Published: January 2020

Cycloheximide and 6-azauridine were employed to study the time course of measles virus protein and nucleic acid syntheses in AV3 cells. Synthesis of ribonucleic acid (RNA) essential for infectivity was first detected at 6 hr and increased concurrently with the formation of essential protein. Maximum levels of virus-specific RNA and protein were present by 18 hr, a time when only 5% of progeny virus was detected. Essential RNA and protein syntheses preceded the formation of infectious virus by at least 10 to 12 hr. The time course of RNA and protein syntheses essential for the formation of complement-fixing (CF) antigen and salt-dependent agglutinin (SDA) was also determined. RNA synthesis essential for the formation of SDA was first detected at 2 hr and was present maximally by 6 hr, whereas SDA-protein increased concurrently with the protein essential for infectivity. This suggested that the last protein essential for infectivity may be SDA. RNA synthesis essential for the formation of CF antigen was first detected at 4 hr, while CF-protein increased at 5 hr and preceded SDA-protein and protein essential for infectivity by approximately 3 hr. Reversal of inhibition of protein synthesis by cycloheximide indicated that early protein synthesis (1 to 3 hr) was required for the formation of infectious virus. The data suggest that the relatively long eclipse period observed with measles virus is related to a long maturation period rather than to late formation of early proteins, viral RNA, or structural proteins.
In Vivo Conversion of the Single-Stranded DNA of the Kilham Rat Virus to a Double-Stranded Form
Authors: Salzman Lois Ann , White Wesley
Published: January 2020

Kilham rat virus (KRV) contains linear, single-stranded DNA in the virion. The fate of radioactive viral DNA was followed after infection of monolayer cells. Within 60 min after infection of cells, 28 to 42% of the parental viral DNA is converted to a new form. This new DNA form is believed to be double stranded and linear on the basis of its sedimentation in neutral and alkaline sucrose gradients, elution from hydroxyapatite columns, its buoyant density in equilibrium CsCl density gradients, and appearance in the electron microscope. The double-stranded linear KRV DNA may be analogous to the replicative form of certain bacteriophages, including φX174, which contain single-stranded circular genomes.
Prophage-Mediated Interference Affecting the Development of
Bacillus subtilis
Bacteriophage φe
Authors: Rettenmier Carl W. , Hemphill H. Ernest
Published: January 2020

Bacteriophage φe shows a reduced efficiency of plating on strains of
Bacillus subtilis
which are lysogenic for the temperate bacteriophage SP02. Although this phenomenon resembles prophage-mediated restriction observed in other bacteria, host-controlled modification of φe was not observed. Mutants of φe which plated with high efficiency on the lysogenic host were isolated.
Physicochemical Studies on L-Cell Virions
Authors: Nichols J. L. , Quade Kristina , Luftig R. B.
Published: January 2020

The L-cell virion (LCV) has been purified from supernatant fluids of mouse L cells grown in suspension culture. The virion is similar to other RNA tumor viruses by several criteria: (i) the density of the virion is 1.16 g/cm
3
; (ii) the virion appears as a rounded membranous particle with an outer diameter of 146.7 ± 11.8 nm, and contains knobs (7-nm diameter) over its surface; (iii) 15 polypeptides (ranging in molecular weight from 7,000 to 110,000) are detectable after electrophoresis of virion protein in sodium dodecyl sulfate-polyacrylamide gels; (iv) three species of RNA can be isolated—high molecular weight (80 to 88
s
) (50%), 7
s
(35%) and 4
s
(15%); (v) heat denaturation of the high-molecular-weight RNA yields a heterogeneous population of molecules (20 to 35
s
) as well as a 7
s
and 4
s
species. Despite the general similarity to infectious RNA tumor viruses, LCV is apparently defective as evidenced by the fact that it does not induce tumors in animals or transform normal mouse cells in vitro (Kindig and Kirsten [17]). The defective nature of the LCV might be related to the fact that assays for DNA polymerase in the virion showed only a negligible activity when compared to Rous sarcoma virus.
Identification of Polysomal RNA in BHK Cells Infected by Sindbis Virus
Authors: Mowshowitz Deborah
Published: January 2020

Polysomes were prepared from Sindbis virus-infected BHK cells. The major species of RNA in these polysomes was identified as 26
S
RNA (interjacent RNA) by (i) disrupting the polysomes with EDTA; (ii) treating the infected cells with puromycin; and (iii) isolating polysomes from cells infected with a temperature-sensitive mutant that does not form nucleocapsids. Small amounts of 42
S
RNA and 33
S
RNA were also found in polysomes.
Virus Replication, Cytopathology, and Lysosomal Enzyme Response of Mitotic and Interphase Hep-2 Cells Infected with Poliovirus
Authors: Bienz Kurt , Egger Denise , Wolff David A.
Published: January 2020

Mitotic Hep-2 cells, selected by the PEL (colloidal silica) density gradient method and held in mitosis with Colcemid, are readily infected by poliovirus type I (Mahoney). They produce and release the same amount of virus as interphase, random-growing cells. In contrast to interphase cells, mitotic cells show no detectable virus-induced cytopathic effect at the light microscopy level and only slight alterations, consisting of small clusters of vacuoles, at the electron microscopy level. Mitotic cells contain the same total amount of lysosomal enzymes per cell as interphase cells, but they display no redistribution of lysosomal enzymes during the virus infection as interphase cells do. This supports the view that lysosomal enzyme redistribution is associated with the cytopathic effect in poliovirus infection but shows that virus synthesis and release is not dependent on either the cytopathic effect or lysosomal enzyme release. The possible reasons for the lack of cytopathic effect in mitotic cells are discussed.
Homologous Viral Interference in
Aedes albopictus
Cultures Chronically Infected with Sindbis Virus
Authors: Stollar Victor , Shenk Thomas E.
Published: January 2020

Complete homologous interference is demonstrated in cultures of
Aedes albopictus
cells chronically infected with Sindbis virus. The interference occurred before there was any detectable RNA synthesis by the superinfecting virus.
Amber Mutant of Bacteriophage Qβ Capable of Causing Overproduction of Qβ Replicase
Authors: Palmenberg Ann , Kaesberg Paul
Published: January 2020

Amber mutant
am
B86 of bacteriophage Qβ is capable of causing the production of five to eight times more viral replicase than wild-type phage. Su
−
bacteria infected with the mutant can carry the viral RNA in a plasmid-like state for many bacterial generations.
Restriction and Modification of Bacteriophage in
Bacillus stearothermophilus
Authors: Lees N. D. , Welker N. E.
Published: January 2020

Host-controlled restriction and modification of TP-1C phage and infectious phage DNA occurs in
Bacillus stearothermophilus
and is subject to control by TP-8 or TP-12 prophage.
Effect of Isotopic Label on Buoyant Density Determinations of Viral DNA in the Preparative Ultracentrifuge
Authors: Cassai Enzo , Bachenheimer Steven
Published: January 2020

The buoyant density of herpes simplex virus DNA may be significantly increased by isotopic labeling, particularly with
14
C. The apparent increase in buoyant density may be readily calculated from the specific activity of the DNA and is easily demonstrated by isopycnic centrifugation in both the preparative and analytical centrifuge.
Studies of Nondefective Adenovirus 2-Simian Virus 40 Hybrid Viruses VII. Characterization of the Simian Virus 40 RNA Species Induced by Five Nondefective Hybrid Viruses
Authors: Levine Arthur S. , Levin Myron J. , Oxman Michael N. , Lewis Andrew M.
Published: January 2020

Five nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses have been isolated and found to contain segments of SV40 DNA covalently linked to Ad2 DNA. The quantity of SV40 DNA present is a stable characteristic of each hybrid virus, and varies from less than 5% (in Ad2
+
ND
3
) to more than 30% (in Ad2
+
ND
4
) of the SV40 genome. We have characterized the SV40 portions of these hybrids by relating the SV40-specific RNA sequences transcribed in cells infected with each hybrid virus to those transcribed in cells infected with each of the other hybrid viruses and with SV40 itself. RNA-DNA hybridization-competition experiments indicate that the number of unique SV40 RNA sequences transcribed in infected cells is proportional to the size of the SV40 DNA segment contained within each hybrid and, in the case of the three hybrids which induce detectable SV40-specific antigens, to the number of SV40 antigens induced. Furthermore, the SV40-specific RNA sequences transcribed from any one of the hybrids are completely represented in the RNA transcribed from all other hybrids with longer SV40 segments. Thus, the SV40 DNA regions in the five hybrid viruses appear to contain some nucleotide sequences in common. The SV40-specific RNA transcribed from Ad2
+
ND
4
, the hybrid containing the largest SV40 segment, is qualitatively similar to the SV40-specific RNA transcribed early (i.e., prior to viral DNA replication) in SV40 lytic infection. Thus, it appears that no significant amount of late SV40 DNA is transcribed during infection by any of the five nondefective Ad2-SV40 hybrid viruses.
Genetic and Immunological Studies of Bacteriophage T4 Thymidylate Synthetase
Authors: Krauss S. W. , Stollar B. D. , Friedkin M.
Published: January 2020

Thymidylate synthetase, which appears after infection of
Escherichia coli
with bacteriophage T4, has been partially purified. The phage enzyme is immunologically distinct from the host enzyme and has a molecular weight of 50,000 in comparison to 68,000 for the host enzyme. A system has been developed to characterize T4
td
mutants previously known to have impaired expression of phage thymidylate synthetase. For this system, an
E. coli
host lacking thymidylate synthetase was isolated. Known genetic suppressors were transduced into this host. The resulting isogenic hosts were infected with phage T4
td
mutants. The specific activities and amounts of cross-reacting material induced by several different types of phage mutants under conditions of suppression or non-suppression have been examined. The results show that the phage carries the structural gene specifying the thymidylate synthetase which appears after phage infection, and that the combination of plaque morphology, enzyme activity assays, and an assay for immunologically cross-reacting material provides a means for identifying true amber mutants of the phage gene.
Cadaverine in Bacteriophage T4
Authors: Astrachan Lazarus , Miller Joan F.
Published: January 2020

Cadaverine was found in bacteriophage T4 when the host cells of
Escherichia coli
K-12 were grown in complex media and aerated by agitation. Only traces of cadaverine were found if the host was grown and agitated in synthetic medium or was aerated by vigorous bubbling in a complex medium. When the host cells were grown anaerobically in a complex medium, cadaverine became the major polyamine in the progeny phage. The polyamine content comprised 80% cadaverine, 14% spermidine (or its recently discovered homologue,
N
-3-aminopropyl-1, 5-diaminopentane), and the remainder putrescine. The conditions that favored appearance of cadaverine are known to be required for induction of lysine decarboxylase. It was shown that lysine was the sole source of bacterial cadaverine.
Suppression of Amber Mutations of Bacteriophage T4 Gene 43 (DNA Polymerase) by Translational Ambiguity
Authors: Karam J. D. , O'Donnell P. V.
Published: January 2020

The growth properties of twelve different amber (
am
) mutants of bacteriophage T4 gene 43 (DNA polymerase) were examined by using nonpermissive (
su
−
) as well as permissive (
su
+
)
Escherichia coli
hosts. It was found that most of these mutants were measurably suppressed in
su
−
hosts by translational ambiguity (misreading of codons during protein synthesis). The ability of these mutants to grow in response to this form of weak suppression probably means that the T4 gene 43 DNA polymerase can be effective in supporting productive DNA replication when it is supplied in small amounts. By similar criteria, studies with other phage mutants suggested that the products of T4 genes 62 (uncharacterized), 44 (uncharacterized), 42 (dCMP-hydroxymethylase), and 56 (dCTPase) are also effective in small amounts. Some T4 gene products, such as the product of gene 41 (uncharacterized), seem to be partially dispensable for phage growth since
am
mutants of such genes do propagate, although weakly, in streptomycin-resistant
su
−
hosts which appear to have lost the capacity to suppress
am
mutations by ambiguity.
Characterization of Two Simian Virus 40-Specific RNA Molecules from Infected BS-C-1 Cells
Authors: Warnaar S. O. , de Mol A. W.
Published: January 2020

Two discrete simian virus 40 (SV40) RNA species sedimenting at 19 and 16
S
, respectively, that are present in infected BS-C-1 cells were characterized with respect to the base composition and the ribonuclease T1 fingerprints. The base composition of the 19
S
SV40 RNA was found to be cytidylic acid (C), 23.0; adenylic acid (A), 28.3; guanylic acid (G), 23.9; and uridylic acid (U), 24.8; that of the 16
S
SV40 RNA was C, 19.3; A, 34.0; G, 22.0; and U, 24.7 mol%. Analysis of the ribonuclease T1 fingerprints indicated a difference in the base sequence of the 19 and 16
S
SV40 RNA. The presence of long sequences of adenylic acid residues (poly A) in these viral RNAs was confirmed.
DNA Replication of Induced Prophage in
Haemophilus influenzae
Authors: Barnhart Benjamin J. , Cox Summers H.
Published: January 2020

DNA synthesis during transition from the lysogenic state to the lytic cycle and throughout the latter has been studied in
Haemophilus influenzae
BC200 (HP1c1). Following exposure to ultraviolet light, there is a 30-min delay in DNA synthesis after which there is a rapidly increasing rate of phage DNA synthesis. The phage genome is replicated without extensive utilization of segments or of breakdown products of the bacterial chromosome. The mode of phage DNA replication was investigated by zonal sedimentation of labeled DNA in 5 to 20% neutral and alkaline sucrose gradients. Tritiated thymidine, incorporated during a 2-min pulse given at 38 min, chases rapidly into DNA, sedimenting like linear DNA of approximately 2 × 10
8
daltons, and then, at the expense of label in this peak, chases into slower-sedimenting phage DNA (2 × 10
7
daltons). The fast-sedimenting, rapidly labeled DNA satisfies certain criteria for being a concatenated replicative intermediate. Observations in the electron microscope revealed linear concatemers in the faster-sedimenting material and circular phage-sized DNA in the slower-sedimenting DNA. When induced cells are gently lysed with lysozyme and Brij 58 to maintain DNA-membrane associations and sedimented in neutral sucrose over a cesium chloride shelf, the concatemer is found with the cell-membrane-wall complex. Membrane-associated label chases to membrane-free material sedimenting like deproteinized HP1c1 DNA. When membrane-associated DNA from the cesium chloride shelf is deproteinized and resedimented in neutral sucrose, the sedimentation profile reveals that sedimentation rates of labeled DNA from this complex are indicative of sizes ranging from 2 × 10
8
daltons down to phage-sized pieces of 2 to 3 × 10
7
daltons. A model is presented which places HP1c1-DNA replication on the cell membrane where a concatemer of phage DNA is synthesized and subsequently degraded to phage-equivalent DNA. Phage-equivalent DNA is then either released from the membrane for packaging or is packaged while still membrane associated. Thus, the cell membrane is not only the site of DNA replication during which phage DNA is synthesized in multiple phage-equivalent concatemers but it is also the site at which these concatemers are selectively reduced to phage-sized pieces.
Induction of Type C Viruses in Cultured Guinea Pig Cells
Authors: Nayak D. P. , Murray Patrick R.
Published: January 2020

Particles morphologically resembling type C viruses were activated by bromodeoxyuridine (BUdR; 10
−4
M) treatment of cultured guinea pig cells. Virus particles were isolated from the cells of normal and leukemic strain 2 and random-bred guinea pigs (adult and embryonic). Immature virus particles with electron-lucent cores were found in the cytoplasmic matrix. The mature particles with electron-dense cores were found outside the cells and some appeared in the process of budding from the plasma membrane. The peak of virus production was observed within 4 days of BUdR treatment. When compared to the amount of virus produced in darkness, visible light enhanced virus production, whereas exposure of BUdR-treated cells to UV light either had no effect or inhibited virus production. Virus particles had a density of 1.16 gm/ml, possessed an oncornavirus-specific reverse transcriptase, and contained a large-molecular-weight RNA (65-70
S
) which dissociated into 36
S
subunits after heat denaturation. The BUdR-activated virus particles, therefore, possessed the morphological, biophysical, and biochemical characteristics of type C oncornaviruses.
In Vitro Protein-Synthesizing Activity of Vesicular Stomatitis Virus-Infected Cell Extracts
Authors: Grubman Marvin J. , Summers Donald F.
Published: January 2020

Crude cytoplasmic extracts from vesicular stomatitis virus (VSV)-infected HeLa cells incorporate radioactive amino acids into hot trichloroacetic acid-precipitable material linearly for 10 to 20 min. The material synthesized in vitro corresponds in molecular weight to four of the five VSV structural proteins. However, synthesis of the viral glycoprotein (G) is significantly reduced, whereas the relative amounts of viral structural proteins L and NS synthesized are increased compared with the ratio of the proteins found in the virion. Fractionation of a VSV-infected crude cytoplasmic extract into a cytoplasmic pellet (20,000 ×
g
for 30 min) and a cytoplasmic supernatant results in a significant reduction in protein synthesizing activity of both fractions, although both contain polysomes. The products synthesized by a cytoplasmic supernatant-directed system included all the VSV structural proteins except the glycoprotein, whereas in an in vitro system directed by the cytoplasmic pellet there is a marked reduction in synthesis of the nucleoprotein (N) and also a small relative increase in synthesis of the glycoprotein. Addition of uninfected, preincubated HeLa or L-cell S10 or a HeLa ribosomal fraction to the VSV-infected cytoplasmic pellet results in a 30- to 60-fold stimulation of
35
S-methionine incorporation. However, these uninfected extracts do not stimulate
35
S-methionine incorporation by the infected crude cytoplasmic extract or the cytoplasmic supernatant. The products synthesized by the stimulated cytoplasmic pellet now include sizeable amounts of the glycoprotein in addition to the other VSV structural proteins.
Mechanism of Oncogenic Transformation by Rous Sarcoma Virus III. Role of Proviral DNA in Morphologic Conversion of Chicken Embryo Fibroblasts
Authors: Balduzzi Piero C.
Published: January 2020

Multiplication of Rous sarcoma virus and morphological conversion of chicken embryo fibroblasts are mediated by a DNA provirus. The role of the provirus in induction of morphological conversion has been shown by experiments of light inactivation of bromodeoxyuridine (BUdR)-sensitized proviral DNA. In the experiments reported here, inactivation of focus formation by BUdR and light could be obtained in cells in which the ability to produce virus has become resistant to X irradiation. This property is considered here to reflect the integrated state of the provirus. These experiments indicate that the role of proviral DNA extends beyond induction of morphological conversion and that an intact provirus is required for the maintenance of the transformed state. These experiments also indicate that no irreversible process leading to morphological conversion is initiated by a nonintegrated or by an integrated provirus.
Effect of a Gene-Specific Suppressor Mutation (
das
) on DNA Synthesis of Gene 46-47 Mutants of Bacteriophage T4D
Authors: Shah D. B. , Berger Hillard
Published: January 2020

Mutants in genes 46 and 47 of bacteriophage T4 exhibit early cessation of DNA synthesis, inability to form a normal rapidly sedimenting DNA intermediate (200
S
), reduced genetic recombination, and reduced viable phage production. A gene-specific suppressor mutation called
das
partially restores many of the pleiotropic effects of gene 46-47 mutants (13). Our results indicate that this partial suppression by
das
is associated with (i) the synthesis of a small fraction of DNA containing long single chains not detectable in 46-47 infection and (ii) a decrease in an “early” function which participates in the degradation of DNA synthesized in the absence of 46-47 functions. However,
das
does not restore the formation of a normal rapidly sedimenting (200
S
) DNA intermediate.
Correlation Between the Antiviral Effect of Interferon Treatment and the Inhibition of In Vitro mRNA Translation in Noninfected L cells
Authors: Falcoff E. , Falcoff R. , Lebleu B. , Revel M.
Published: January 2020

When noninfected L-cell suspension cultures are treated with interferon (specific activities superior to 10
6
reference units per mg of protein), the cell-free cytoplasmic extracts obtained are inactive for the translation of exogenous natural mRNAs. The dose-response curve shows that comparable amounts of interferon are required to produce a 50% reduction of Mengo virus multiplication in vivo and Mengo RNA translation in vitro. With higher doses of interferon, Mengo RNA translation is completely abolished, while poly U translation and endogenous protein synthesis are only slightly affected. The inactivation of Mengo RNA translation is reversible; after removal of interferon, normal translation activity is regained together with the ability to support Mengo virus multiplication. Fractionation of the cell-free extracts shows that the effect is localized in the fraction which can be washed off the ribosomes by high salt. These results establish that interferon induces a block in genetic translation in noninfected L cells.
Purification, Characterization, and Comparison of the DNA Polymerases from Two Primate RNA Tumor Viruses
Authors: Abrell John W. , Gallo Robert C.
Published: January 2020

The DNA polymerase from the Mason-Pfizer monkey virus (M-PMV), an RNA tumor virus not typical type-C or type-B, has been purified a thousand-fold over the original crude viral suspension. This purified enzyme is compared to a similarly purified DNA polymerase from the primate woolly monkey virus, a type-C virus. The two enzymes have similar template specificities but differ in their requirements for optimum activity. Both DNA polymerases have a pH optimum of 7.3 in Tris buffer. M-PMV enzyme has maximum activity with 5 mM Mg
2+
and 40 mM potassium chloride, whereas the woolly monkey virus optima are 100 mM potassium chloride with 0.8 mM Mn
2+
. The apparent molecular weight of the M-PMV enzyme is approximately 110,000, whereas the woolly monkey virus polymerase is approximately 70,000. The biochemical properties of these two enzymes were also compared to a similarly purified enzyme from a type-C virus from a lower mammal (Rauscher murine leukemia virus). The results show that more similarity exists between the DNA polymerases from viruses of the same type (type-C), than between the polymerases from viruses of different types but from closely related species.
Chromatographic Analyses of Isoaccepting tRNAs from Avian Myeloblastosis Virus
Authors: Gallagher Robert E. , Gallo Robert C.
Published: January 2020

Avian myeloblastosis virus (AMV) 4
S
RNA was tested for amino acid acceptor activity for 18 of the 20 amino acids. A nonrandom distribution of viral tRNAs was found compared with tRNA from normal liver or from AMV-infected leukemic myeloblasts, confirming previous reports. Methionine and proline tRNAs were considerably enriched, whereas glutamic acid, glutamine, serine, tyrosine, and valine tRNAs were markedly depleted in AMV relative to homologous cellular tRNAs. The seven AMV tRNAs with the greatest amino acid acceptance capacities, which were in order methionine, proline, lysine, arginine, histidine, isoleucine, and threonine tRNAs, were compared with homologous tRNAs from leukemic myeloblasts and liver by reversed-phase 5 chromatography. Of the 25 isoaccepting chromatographic fractions identified, no tRNA species unique to AMV was detected. Only methionyl-tRNA showed a substantial quantitative variation in isoaccepting species compared with the host cell. Thus, viral selectivity for amino acid-specific tRNAs is not, generally, paralleled by selectivity for individual isoaccepting tRNA species. Qualitative differences in arginyl- and histidyl-tRNA isoaccepting species were discovered in virus and leukemic myeloblasts compared with liver. This indicates the existence of structural differences in these tRNA species which could be related to virus replication or expression.
Selection of Temperature-Sensitive Mutants During Persistent Infection: Role in Maintenance of Persistent Newcastle Disease Virus Infections of L Cells
Authors: Preble Olivia T. , Youngner Julius S.
Published: January 2020

Virus mutants (NDV
pi
) recovered from L cells persistently infected with Newcastle disease virus (NDV, Herts strain) are temperature-sensitive (ts) at 43 C, although the wild-type virus (NDV
o
) which initiated the persistent infection replicates normally at that temperature. To study the relationship between the ts marker of NDV
pi
and the other properties which distinguish this virus from NDV
o
, NDV
pi
ts
+
revertants were selected at the nonpermissive temperature and NDV

o

ts mutants were generated by treating NDV

o

with nitrous acid. Spontaneously-occurring ts mutants in the Herts NDV population were also isolated. The different virus populations were characterized with regard to plaque size, virulence for eggs, and thermal stability of infectivity, hemagglutinin, and neuraminidase. The NDV
pi
ts
+
revertants, although no longer temperature-sensitive, retained NDV
pi
properties, whereas both spontaneously-occurring and mutagen-induced ts mutants remained wild-type in their other properties. These findings showed that the properties which characterized NDV
pi
were independent of the ts marker. However, the ts marker and the other markers of NDV
pi
were coselected during the persistent infection, and the combination of those markers appeared to be important in the outcome of NDV infection of L cells. NDV
pi
replicated productively in L cells, whereas NDV
o
, the NDV
pi
ts
+
revertants, and the spontaneously-occurring ts mutants all yielded covert infections in L cells. The role of the selection of ts mutants in persistent infection was confirmed as follows: L cells were persistently infected with NDV
pi
ts
+
revertants and NDV
o
ts mutants. Virus recovered from the persistently infected cultures after eight cell passages was always temperature-sensitive and of smaller plaque size than the parental virus in chicken embryo cell cultures. Similar results were obtained with virus recovered from L-cell cultures persistently infected with two other velogenic strains of NDV, the Texas-GB and Kansas-Man strains. These results strongly suggest that selection of ts mutants during the persistent infection was not random and played a role in establishment or maintenance of the persistent infection, or both.
Acquisition of Sequences Homologous to Host DNA by Closed Circular Simian Virus 40 DNA III. Host Sequences
Authors: Rozenblatt Shmuel , Lavi Sara , Singer Maxine F. , Winocour Ernest
Published: January 2020

A preparation of serially passaged simian virus 40 (SV40) DNA, in which at least 66% of the molecules contain covalently linked cellular DNA sequences, was digested to completion with the
Hemophilus influenzae
restriction endonuclease. Polyacrylamide gel electrophoresis of the digest showed that the majority of the cleavage products migrated as nine classes of fragments, each class defined by a particular molecular weight. These classes of fragments differ in molecular weight from the fragments produced by the action of the same enzyme on plaque-purified virus DNA. Three classes of fragments were present in less than equimolar amounts relative to the original DNA. The remaining six classes of fragments each contain more than one fragment per original DNA molecule. DNA-DNA hybridization analysis (using the filter method) of the isolated cleavage products demonstrated the presence of highly reiterated cell DNA sequences in two of the nine classes of fragments. A third class of fragments hybridized with high efficiency only to serially passaged SV40 DNA; the level of hybridization to plaque-purified virus DNA was low and there was essentially no hybridization with cell DNA immobilized on filters. It is suggested that this class of fragments contains unique host sequences. It was estimated that at least 27% of the sequences in the substituted SV40 DNA molecules studied are host sequences. The majority of these are probably of the nonreiterated type.
Separation of DNA Sequences Complementary to the RNA of Avian Myeloblastosis Virus from Chicken DNA by Alkaline Cesium Chloride Density Sedimentation
Authors: Shoyab M. , Baluda M. A.
Published: January 2020

Density gradient sedimentation in alkaline cesium chloride of DNA from normal chicken embryos or leukemic myeloblasts fragmented to a size of 13
S
revealed that the DNA sequences complementary to 70
S
avian myeloblastosis virus RNA sedimented in the high guanine plus cytosine region ahead of the main peak of cellular DNA. When the DNA was fragmented into pieces of 6.6
S
there was a broader distribution of the DNA sequences complementary to the viral RNA. This technique could be employed as a step towards the isolation of DNA copies of the entire viral RNA genome from the mass of host cellular DNA.
Envelope of Mouse Mammary Tumor Virus Studied by Freeze-Etching and Freeze-Fracture Techniques
Authors: Sheffield Joel B.
Published: January 2020

As part of a study of the cell surface changes associated with the production of murine mammary tumor virus, the structure of the envelope of this virus has been examined by using freeze-fracture techniques. Both fracture and deep-etch surfaces were examined. The fracture faces contain 10-nm spheres comparable to those observed on fractured plasma membranes, although fewer in number. Surfaces exposed by etching possess a highly regular hexagonal array of pits 25 nm apart. By examining freeze-fracture and freeze-etch preparations of virus with ferritin covalently bound to its surface, it has been determined that the surface exposed by etching is the outer surface of the virus. The pitted exterior surface of the mammary tumor virus appears to be a unique surface structure.
Mapping of Simian Virus 40 Early Functions on the Viral Chromosome
Authors: Morrow John F. , Berg Paul , Kelly Thomas J. , Lewis Andrew M.
Published: January 2020

The simian virus 40 (SV40) DNA segment in the nondefective adenovirus 2-SV40 hybrid, Ad2
+
ND
4
, is colinear with the segment between 0.11 and 0.59 SV40 fractional length from the site at which the R
1
restriction endonuclease cleaves SV40 DNA. This specifies the region of the SV40 DNA molecule which induces the early SV40 antigens: U antigen, tumor specific transplantation antigen, and T antigen. A variant of Ad2
+
ND
4
, called Ad2
+
ND
4del
, was found which has a deletion of the DNA segment between 0.50 and 0.57 SV40 fractional length from the R
1
endonuclease cleavage point.
Improved Technique for the Isolation of Temperature-Sensitive Mutants of Foot-and-Mouth Disease Virus
Authors: Lake J. , Mackenzie J. S.
Published: January 2020

An improved temperature-shift selection and screening method is described for the isolation of temperature-sensitive mutants of foot and mouth disease virus.
Genetic and Physiological Properties of Temperature-Sensitive Mutants of Cocal Virus
Authors: Pringle C. R. , Wunner W. H.
Published: January 2020

Temperature-sensitive (
ts
) mutants of Cocal virus (VSV Cocal) were isolated after treatment with the base analogue mutagen, 5-fluorouracil. These mutants could be classified into four mutually complementing groups. Weak complementation was detected between certain pairs of VSV Cocal
ts
mutants and
ts
mutants of vesicular stomatitis virus (VSV) Indiana, but no complementation was observed with
ts
mutants of VSV New Jersey. Two complementing
ts
mutants of Chandipura virus, an unrelated rhabdovirus, did not complement any VSV mutant, Thus, ability to complement in the VSV group appears to be correlated with serological relationships.

The RNA and protein-synthesizing capacities of these
ts
mutants have been determined, and it is possible to establish a correspondence between the VSV Cocal and the VSV Indiana complementation groups.
Phosphorylation of Simian Virus 40 Proteins in a Cell-Free System
Authors: Tan K. B. , Sokol F.
Published: January 2020

We have shown previously that all the structural proteins of simian virus 40 (SV40) are phosphoproteins. Virus phosphorylated in vivo could be further phosphorylated with exogenous cellular protein kinases in a cell-free system containing γ-
32
P-ATP as phosphate donor. In intact infectious virus only polypeptides 1 and 2 (mol wt 49,000 and 40,800, respectively) were further phosphorylated in vitro. However, when infectious SV40 was partially disrupted, treated with nucleases, and then phosphorylated in vitro, all five structural polypeptides accepted additional phosphate groups. Similarly, all polypeptides of intact empty capsids, derived from infected cells, were further phosphorylated in vitro. Phosphorylation of empty capsids and infectious SV40 in vitro was enhanced from 4- to 11-fold after prior treatment of virus with alkali. The phosphate group was linked only to serine residues of the viral polypeptides phosphorylated both in vitro and in vivo.
Integrated State of Oncornavirus DNA in Normal Chicken Cells and in Cells Transformed by Avian Myeloblastosis Virus
Authors: Markham P. D. , Baluda M. A.
Published: January 2020

The covalent linkage of oncornavirus-specific DNA to chicken DNA was investigated in normal chicken embryo fibroblasts (CEF) and in virus-producing leukemic cells transformed by avian myeloblastosis virus (AMV). The virus-specific sequences present in cellular DNA fractionated by different methods were detected by DNA-RNA hybridization by using 70
S
AMV RNA as a probe. In CEF and in leukemic cells, the viral DNA appeared to be present only in the nucleus. After cesium chloride-ethidium bromide density equilibrium sedimentation, the viral DNA was present as linear, double-stranded molecules not separable from linear chicken DNA. After extraction by the Hirt procedure, the viral DNA precipitated with the high-molecular-weight DNA. After alkaline sucrose velocity sedimentation, the viral DNA cosedimented with the high-molecular-weight cellular DNA. The results indicate that in both types of cells studied, the oncornavirus-specific DNA sequences were linked by alkali stable bonds to nuclear cellular DNA of high molecular weight and did not appear to be present in free form of any size.
Minicells of
Bacillus subtilis:
a New Bacteriophage-Blocking Agent
Authors: Reeve John N. , Mendelson Neil H.
Published: January 2020

Bacteriophage SP01, SP17, and φ29 rapidly absorb irreversibly to minicells of
Bacillus subtilis
but do not produce a lytic cycle in minicells.
Reassociation Kinetics for Epstein-Barr Virus DNA: Nonhomology to Mammalian DNA and Homology of Viral DNA in Various Diseases
Authors: Kawai Yasuo , Nonoyama Meihan , Pagano Joseph S.
Published: January 2020

The number of Epstein-Barr virus (EBV) genomes per cell in established leukocytic lines and tissue specimens has been evaluated by measuring DNA-DNA reassociation kinetics with hydroxyapatite chromatography. Under the proper conditions, this method is sufficiently sensitive to detect EBV DNA in the amount of 0.1 genome per cell. All the samples tested that have been suspected to be without EBV DNA by cRNA hybridization proved negative by this more sensitive specific analysis. These included Hela and Hep2 cells, a negative case of Burkitt's lymphoma, two negative cases of nasopharyngeal carcinoma, and two established human leukocytic lines. Homology tests conducted with single-strand-specific nuclease S1 indicated that the viral DNA from a nasopharyngeal carcinoma and infectious mononucleosis were more than 90% homologous to EBV DNA.
Alteration in tRNA Methyltransferase Activity in Mengovirus Infection: Host Range Specificity
Authors: Wilkinson Ray , Kerr Sylvia J.
Published: January 2020

The tRNA methyltransferase activity in mengovirus-infected L cells, HeLa cells, and Maden Derby bovine kidney cells has been examined during the course of infection. The first two cell lines yield a productive infection, but have different kinetics of inhibition of host RNA synthesis, whereas the bovine kidney cells are a restrictive host. In infected L cells the enzymes show altered capacity and base specificity throughout the infection. In infected HeLa cells and in infected bovine kidney cells less marked changes were seen. No inhibitors or activators of the enzymes were detected in any of the infected cell lines. Labeling experiments in infected cells indicated that in infected L cells synthesis of RNA was inhibited to a greater degree than was methylation of RNA. The consequence of this would be a hypermethylation of RNA. The methylated derivatives synthesized in infected L cells showed changes in relative proportions. Infection of HeLa cells and bovine kidney cells did not show such marked effects on methylation of RNA.
Synthesis of the Unusual DNA of
Bacillus subtilis
Bacteriophage SP-15
Authors: Neubort Simon , Marmur Julius
Published: January 2020

Cultures of
Bacillus subtilis
infected with phage SP-15 were examined to investigate the metabolic origin of two of the unique components of the phage DNA: the component responsible for the unusually high buoyant density in CsCl and the unusual pyrimidine, 5-(4′, 5′-dihydroxypentyl) uracil (DHPU). Newly synthesized pulse-labeled DNA was light in buoyant density and shifted to the high density of mature phage DNA upon further incubation. Parental DNA was converted to a light-density intermediate form prior to replication. When labeled uracil, thymidine, or DHPU were added to infected cells, it was found that only uracil served as the precursor to DHPU and thymine in phage DNA. Analysis of the bases from hydrolyzed DNA of labeled phage or infected cells indicated that the uracil was incorporated into the DNA as such (presumably via deoxyuridine triphosphate) and later converted to DHPU and thymine at the macromolecular level. The sequence of events after phage infection appeared to be: (i) injection of parental DNA; (ii) conversion of parental DNA to a light form; (iii) DNA replication, yielding light DNA containing uracil; (iv) conversion of uracil to DHPU and thymine; and (v) addition of the heavy component.
Arrangement on the Chromosome of the Known Pre-Early Genes of Bacteriophages T5 and BF23
Authors: Beckman L. David , Anderson Gerry C. , McCorquodale D. J.
Published: January 2020

Genetic crosses between mutants defective in the known pre-early genes of T5 and BF23 and the detection of putative N-terminal fragments have allowed the determination of the order of genes along the initially transferred 8% section of DNA of these phages.
Reactivation of Photoinactivated Single-Stranded DNA Bacteriophage φX174 by UV-Irradiated
Escherichia coli
Cells
Authors: Bandopadhyay Uma , Poddar Ramendra K.
Published: January 2020

Reactivation of single-stranded DNA phage, photodynamically inactivated in the presence of proflavine sulfate, by three isogenic
Escherichia coli
strains having different DNA repair capabilities has been studied. It was found that reactivation of photoinactivated φX174 was possible only if the host cells were recombination proficient (
recA
+
) and had been lightly irradiated with UV light prior to infection; the presence of the
uvrA
+
gene was not essential. Only a small part of the proflavine-mediated photodynamic damage in φX174 could be repaired in this fashion. Burst sizes of reactivated phages were, however, comparable to those of normal unirradiated phages.
Restricted Replication of Vesicular Stomatitis Virus in Human Lymphoblastoid Cells
Authors: Nowakowski Maja , Bloom Barry R. , Ehrenfeld Ellie , Summers Donald F.
Published: January 2020

Replication of vesicular stomatitis virus (VSV) is restricted in one human lymphoblastoid cell line (Raji), but not in another similar cell line (Wil-2), compared with growth in HeLa cells. This restriction is characterized by a low proportion of cells yielding infectious virus and is associated with limited production of 42
S
virion RNA. Primary transcription of 13
S
and 26
S
VSV-specific RNA is not restricted in Raji cells, and the 13
S
RNA produced contains adenylate-rich sequences. This suggests that the block in Raji cells involves some step required for the replication of virion RNA.
Detection of Viral DNA Sequences in Adenovirus-Transformed Cells by In Situ Hybridization
Authors: Loni Maria Carla , Green Maurice
Published: January 2020

Cytological preparations of cells transformed by members of three groups of human adenoviruses, adenovirus 12, 7, and 2, were annealed with radioactive complementary RNA (cRNA) (4 × 10
7
to 4.5 × 10
7
dpm/μg) prepared by copying viral DNA with the
Escherichia coli
DNA-directed RNA polymerase. These in situ hybridizations detected adenovirus-specific DNA sequences in interphase nuclei when transformed cells were annealed with homologous viral cRNA, but not with heterologous viral cRNA. The highest autoradiographic grain counts were found over adenovirus 7-transformed cell nuclei, next over adenovirus 12-, and the lowest over adenovirus 2-transformed cell nuclei. This is the same order as found by reassociation kinetic measurements (K. Fujinaga and M. Green, unpublished data).
Lack of Sequence Homology Among RNAs of Avian Leukosis-Sarcoma Viruses, Reticuloendotheliosis Viruses, and Chicken Endogenous RNA-Directed DNA Polymerase Activity
Authors: Kang Chil-Yong , Temin Howard M.
Published: January 2020

The relatedness of the RNAs of the three avian systems, including six avian leukosis-sarcoma viruses, four reticuloendotheliosis viruses, and the microsome fraction of normal uninfected chicken embryo cells, containing RNA and a DNA polymerase have been studied by nucleic acid hybridization. All six avian leukosis-sarcoma viruses have closely related nucleotide sequences; and all four reticuloendotheliosis viruses have closely related nucleotide sequences. But, almost no similarities were detected between the RNAs of avian leukosis-sarcoma viruses and reticuloendotheliosis viruses. The RNA template of the endogenous RNA-directed DNA polymerase activity of normal uninfected chicken cells had no detectable relationship to RNAs of avian leukosis-sarcoma and reticuloendotheliosis viruses.
Nucleic Acid Synthesis in Cytoplasm of Yaba Monkey Tumor Virus-Infected Cells
Authors: Rouhandeh H. , Rouhandeh M. L.
Published: January 2020

Yaba tumor virus progeny appeared in cynomolgus monkey kidney cells at 24 h postinfection and reached a plateau at 72 h in the first cycle of replication. Viral DNA synthesis was first detected at about 3 h and reached a peak in 18 h. Maximum coating of viral DNA in infected cells occurred at 4 days postinfection. Rapidly labeled RNA was synthesized in the cytoplasm of virus-infected cells. At 6 h postinfection 7 to 10
S
RNA was present; this species was present in greater amount at 12 h; at 24 h a truncated peak indicated the presence of 14 to 15
S
as well as 7 to 10
S
RNA. Hybridization data indicated that the largest peak of messenger RNA synthesis occurred at 11 to 13 h postinfection and a second, slightly smaller, peak occurred at 21 to 23 h.
Translation of Virus mRNA: Synthesis of Bacteriophage Qβ Proteins in a Cell-Free Extract from Wheat Embryo
Authors: Davies Jeffrey W. , Kaesberg Paul
Published: January 2020

The RNA from bacteriophage Qβ can be translated by cell-free extracts from wheat embryos. This translation, by 80
S
ribosomes, occurs at a low magnesium ion concentration. Three products are synthesized which coelectrophorese with Qβ proteins synthesized in
Escherichia coli
extracts. The smallest of these has been identified as coat protein. Although the polycistronic bacteriophage message is translated with fidelity, the efficiency is much less than when the monocistronic brome mosaic virus coat protein message is translated.