bluuebunny/crossref_metadata_2025 huggingface dataset:
Murine Mammary Tumor Virus Expression During Mammary Tumorigenesis in BALB/c Mice
Authors: Pauley Robert J. , Medina Daniel , Socher Susan H.
Published: January 2020

Steady-state levels of murine mammary tumor virus (MuMTV) RNA were quantitated during mammary tumorigenesis in BALB/c mice by molecular hybridization with a representative MuMTV complementary DNA (cDNA) probe. Hyperplastic alveolar nodule (HAN) lines are preneoplastic mammary lesions that were induced in BALB/c mice by hormones alone or in combination with 7,12-dimethylbenz(a)anthracene and give rise to mammary tumors. The hormone-induced HAN lines D1 and D2 contained detectable amounts of hybridizable MuMTV sequences. MuMTV RNA sequences were also observed in five of the six transplanted BALB/c mammary tumors that were examined. Similar levels of hybridizable MuMTV RNA were observed between the D1 or D2 HAN line and mammary tumors derived from each HAN line. The D2 HAN line as well as D2, C4, and CD8 mammary tumors accumulated RNA that was apparently homologous to most of the MuMTV genome. Thermal denaturation of hybrids indicated extensive sequence homology between the MuMTV cDNA and hybridizable RNA in the BALB/c HAN lines and mammary tumors. A low level of type C viral RNA was observed in the BALB/c HAN lines and most mammary tumors by molecular hybridization with a cDNA to Moloney murine leukemia virus. These data demonstrate that MuMTV sequences are frequently expressed in hormone-induced BALB/c HAN lines and mammary tumors derived from HAN lines or ductal hyperplasias induced in BALB/c mice by hormones and/or a chemical carcinogen. The transition from the preneoplastic to the neoplastic state in BALB/c mice does not appear to be due to a change in the steady-state levels of MuMTV RNA since the hormone-induced HAN lines and mammary tumors had similar levels of hybridizable MuMTV RNA.
Simian virus 40 T- and U-antigens: immunological characterization and localization in different nuclear subfractions of simian virus 40-transformed cells
Authors: Deppert W
Published: January 2020

Simian virus 40 (SV40)-transformed cells and cells infected by the nondefective adenovirus 2(Ad2)-SV40 hybrid viruses Ad2+ND1 and Ad2+ND2 were analyzed for SV40 T- and U-antigens, respectively, using individual hamster SV40 tumor sera or serum for which U-antibodies were removd by absorption. These studies showed that (i) T- and U-antigens can be defined by separate classes of antigenic determinants and (ii) the U-antigenic determinants in SV40-transformed cells and in hybrid virus-infected cells are similar. The apparent discrepancy in the subcellular location of U-antigen in SV40-transformed cells (nuclear location) and in hybrid virus-infected cells (perinuclear location) as determined by immunofluorescence staining of methanol/acetone-fixed cells could be resolved by treating hybrid virus-infected cells with a hypotonic KCl solution before fixation. Upon this treatment hybrid virus-infected cells also showed nuclear U-antigen staining. The possibility of an association of T- and U-antigens with different nuclear subfractions in SV40-transformed cells was investigated. Detergent-cleaned nuclei of SV40-transformed cells were fractionated into nuclear matrices and a DNase-treated, high-salt nuclear extract. Analysis of the nuclear matrices by immunofluorescence microscopy with T+U+ and T+U- hamster SV40 tumor serum revealed that U-antigen remained associated with the nuclear matrices, whereas T-antigen could not be detected in this nuclear subfraction. T-antigen, however, could be immunoprecipitated from nuclear extracts of the SV40-transformed cells.
Oligonucleotide mapping studies of standard and defective Sindbis virus RNA
Authors: Dohner D , Monroe S , Weiss B , Schlesinger S
Published: January 2020

Oligonucleotide mapping studies of the RNA from standard and defective interfering particles of Sindbis virus demonstrate that 3'- and 5'-terminal regions of the genome are conserved in the defective RNAs. These studies also suggest that defective RNAs contain multiple deletions.
Chromosomal location of the attachment site for the PA-2 prophage in Escherichia coli K-12
Authors: Pugsley A P , Littmann-Louth D , Schnaitman C A
Published: January 2020

The chromosomal attachment site for the PA-2 prophage is located between dsd and aroC at the approximately 50 min on the Escherichia coli K-12 genetic map. The attachment site is designated attPA-2.
Quantitative measurement of intracellular RNA genomes of Rauscher murine leukemia virus by competition hybridization in DNA excess
Authors: East J L , Chan J C , Bartlett R J , Knesek J E
Published: January 2020

The technique of competition hybridization in DNA excess was used to determine the intracellular distribution of RNA genomes of Rauscher murine leukemia virus. An examination of subcellular RNA fractions revealed that 59% of intracellular viral RNA genomes were associated with the nuclear-enriched fraction, 41% with the cytoplasmic fraction, and 18% with the polysomal-enriched fraction. Also, an analysis of total cellular RNA disclosed that 20% of intracellular viral RNA genomes were polyadenylated and 80% were not polyadenylated.
Transforming Region of Group A, B, and C Adenoviruses: DNA Homology Studies with Twenty-Nine Human Adenovirus Serotypes
Authors: Mackey Jesse K. , Wold William S. M. , Rigden Patricia , Green Maurice
Published: January 2020

The 31 human adenovirus (Ad) serotypes form five groups based upon DNA genome homologies: group A (Ad12, 18, 31), group B (Ad3, 7, 11, 14, 16, 21), group C (Ad1, 2, 5, 6), group D (Ad8, 9, 10, 13, 15, 17, 19, 20, 22-30), and group E (Ad4) (M. Green, J. Mackey, W. Wold, and P. Rigden, Virology, in press). Group A Ads are highly oncogenic in newborn hamsters, group B Ads are weakly oncogenic, and other Ads are nononcogenic. However, most or all Ads transform cultured cells. We have studied the homology of Ad5, Ad7, and Ad12 transforming restriction endonuclease DNA fragments with DNAs of 29 Ad types. Ad5
Hin
dIII-G (map position 0-7.3), Ad7
Xho
I-C (map position 0-10.8), and Ad12 (strain Huie)
Eco
RI-C (map position 0-16) and
Sal
I-C (map position 0-10.6) fragments were purified, labeled in vitro (nick translation), and annealed with DNAs of Ad1 to Ad16, Ad18 to Ad24, and Ad26 to Ad31. Hybrids were assayed by using hydroxylapatite. Ad5
Hin
dIII-G hybridized 98 to 100% with DNAs of group C Ads, but only 1 to 15% with DNAs of other types. Ad7
Xho
I-C fragment hybridized 85 to 99% with DNAs of group B Ads, but only 6 to 21% with DNAs of other types. Ad12 (Huie)
Eco
RI-C hybridized 53 to 68% with DNAs of five other Ad12 strains, 53% with Ad18 DNA, 56% with Ad31 DNA, but only 3 to 13% with DNAs of other types. In vitro-labeled Ad12 (Huie)
Sal
I-C hybridized 35 to 71% with DNAs of 6 other Ad12 strains, 44% with Ad18 DNA, 52% with Ad31 DNA, but only 2 to 7% with DNAs Ad7, Ad2, Ad26, or Ad4. When assayed using S-1 nuclease,
Sal
I-C annealed 17 to 44% with DNAs of group A Ads. The melting temperatures of the hybrids of Ad5
Hin
dIII-G with all group C Ad DNAs were 84°C in 0.12 M sodium phosphate (pH 6.8). The melting temperature of the Ad12 (Huie)
Eco
RI-C hybrid with Ad12 (Huie) DNA was 83°C, but was only 71 to 77°C with DNAs of other group A Ads. Thus, group C and group B Ads both have very homologous transforming regions that are not represented in DNAs of non-group C Ads or non-group B Ads, respectively. Similarily, group A Ads have unique but less homologous transforming regions. These different transforming nucleotide sequences may be reflected in the different oncogenic properties of group A, B, and C Ads.
Structure and origin of defective genomes contained in serially passaged herpes simplex virus type 1 (Justin)
Authors: Locker H , Frenkel N
Published: January 2020

Restriction enzyme and hybridization analyses have revealed that high-density DNA prepared from passage 15 of serially passaged herpes simplex virus type 1 (Justin) contains three major classes of modified viral DNA molecules, each composed of distinct but closely related types of repeate units. The DNA sequences within the three types of repeat units are colinear with the DNA sequences located at the right end (between coordinates 0.94 and 1.0) of the parental herpes simplex virus type 1 genome. Thus, the three types of repeat units each contain the entire repeat sequence (ac) (which brackets the unique sequences of the small [S] component of herpes simplex virus type 1 DNA) and differ only with respect to the amount of unique S sequences which they contain. The three classes of high-density DNA molecules were found to be stably propagated between passages 6 and 15 of this series.
Cell-free synthesis of mouse mammary tumor virus Pr77 from virion and intracellular mRNA
Authors: Dahl H H , Dickson C
Published: January 2020

Mouse mammary tumor virus (MuMTV) was purified from two cell lines (GR and Mm5MT/c1), and the genomic RNA was isolated and translated in vitro in cell-free systems derived from mouse L cells and rabbit reticulocytes. The major translation product in both systems was a protein with the molecular weight 77,000. Several other products were also detected, among them a 110,000-dalton and in minor amounts a 160,000-dalton protein. All three polypeptides were specifically immunoprecipitated by antiserum raised against the major core protein of MuMTV (p27), but they were not precipitated by antiserum against the virion glycoprotein gp52. Analysis of the in vitro products by tryptic peptide mapping established their relationship to the virion non-glycosylated structural proteins. The 77,000-dalton polypeptide was found to be similar, if not identical, to an analogous precursor isolated from MuMTV-producing cells. Peptide mapping of the 110,000-dalton protein shows that it contains all of the methionine-labeled peptides found in the 77,000-dalton protein plus some additional peptides. We conclude that the products synthesized in vitro from the genomic MuMTV RNA are related to the non-glycosylated virion structural proteins. Polyadenylic acid-containing RNA from MuMTV-producing cells also directed the synthesis of the 77,000-dalton polypeptide in the L-cell system. If this RNA preparation was first fractionated by sucrose gradient centrifugation the 77,000-dalton protein appeared to be synthesized from mRNA with a sedimentation coefficient between 25 and 35S.
In Vitro Selection of High-Infectious, Leukemogenic Virus from Low-Infectious, Non-Leukemogenic Type C Virus from a Malignant ST/a Mouse Cell Line
Authors: Willumsen Berthe M.
Published: January 2020

Low-infectious, nontransforming type C virus was isolated from an in vitro spontaneously transformed ST/a mouse cell line, ST-L1. The virus released by ST-L1 cells was NB-tropic and XC
−
. It gave rise to very small peroxidase antibody plaques (PAP) in cultures which initially were nonproducing. Sodium dodecyl sulfate (SDS)-polyacrylamide gels of the structural proteins of the ST-L1 virus showed an envelope glycoprotein with an apparent mass of 65 kilodaltons (kdal). The mouse cells SC-1, BALB/3T3, and NIH/3T3 could be productively infected with cell-free supernatants from the ST-L1 cell line; however, virus was detected in supernatant fluids only after two to four subcultures of the infected cells. The virus thus produced was XC
+
and a large plaque former. The virus released from infected SC-1 cells was N-tropic, whereas the viruses from infected NIH/3T3 and BALB/3T3 cells were NB-tropic. The structural proteins of the N- and NB-tropic viruses could be distinguished on SDS polyacrylamide gels, the major dissimilarity being a difference in the mobility of the p30. All these viruses had an envelope glycoprotein with an apparent mass of 70 kdal. The infectivity of the viruses, measured as PAP per nanogram of p30, was 30- to 60-fold lower for the virus released from the ST-L1 cell line than that of the viruses after passage in SC-1, NIH/3T3, and BALB/3T3 cells. None of the viruses could infect rabbit or mink cells. Inoculation of the viruses into newborn mice showed that the ST-L1 virus was non-leukemogenic, whereas the NB-tropic virus selected from this after passage in BALB/3T3 or NIH/3T3 cells was highly leukemogenic. Viruses isolated from leukemic animals were indistinguishable with respect to host range and protein mobilities in SDS gels from the ones with which the mice were inoculated. Although the SC-1-selected virus was highly infectious in vitro, it was only weakly, if at all, leukemogenic.
Comparison of the small RNAs of polymerase-deficient and polymerase-positive Rous sarcoma virus and another species of avian retrovirus
Authors: Sawyer R C , Hanafusa H
Published: January 2020

The small RNAs contained in virions of avian leukosis and sarcoma viruses are a virus-specific subset of the total small RNA population of the host cell. The reverse transcriptase protein must be present in the budding virion for this selection to take place. Virions of the alpha form of the Bryan strain of Rous sarcoma virus, which lack detectable reverse transcriptase, incorporated an unselected population of small RNAs identical to total chicken cell small RNA. Virions of reticuloendotheliosis virus, which contain a reverse transcriptase unrelated to that of the avian leukosis and sarcoma viruses, contained a distinctly different population of small RNAs although both the avian leukosis and sarcoma and the reticuloendotheliosis viruses were grown in chicken cells. Because the primer for avian leukosis and sarcoma virus RNA-dependent DNA synthesis is a host cell tRNA, the differences in reverse transcriptase small RNA selection may help explain the failure of different species of retrovirus to complement for the reverse transcriptase.
Regulation of simian virus 40 early and late gene transcription without viral DNA replication
Authors: Birkenmeier E H , Chiu N , Radonovich M F , May E , Salzman N P
Published: January 2020

Primary cultures of African green monkey kidney cells were infected with the simian virus 40 temperature-sensitive mutant tsA58 at the nonpermissive temperature of 41 degrees C for 12 to 20 h. Under these conditions, a defective T antigen was produced and no viral DNA replication was detected. Viral transcription complexes were extracted from infected nuclei using Sarkosyl and the nascent chains of RNA elongated in vitro. Sixty to 70% of the viral RNA synthesized in vitro hybridized to late gene sequences. In contrast, 80 to 90% of the nuclear viral RNA labeled in vivo during a 15-min pulse with [3H]uridine hybridized to early gene sequences. This suggests that selective degradation of late gene transcripts occurs in vivo. The role of T antigen and viral DNA replication in regulation of simian virus 40 transcription is discussed.
Mapping of a Temperate Bacteriophage Active on
Bacillus subtilis
Authors: Rutberg Lars
Published: January 2020

Bacteriophage φ105 is a temperate bacteriophage for
Bacillus subtilis
168. Temperature-sensitive and plaque mutants of φ105 were isolated. The results of two- and three-factor crosses with these mutants suggest the vegetative map of φ105 to be circular. The location of prophage φ105 between bacterial markers
phe-1
and
ilvA1
was shown by means of PBS1 transduction. Five markers in the prophage were linearly ordered with respect to the bacterial markers. Linkage between bacterial and prophage markers was demonstrated in transformation experiments with deoxyribonucleic acid extracted from lysogenic bacteria. The data demonstrate that prophage φ105 is linearly inserted into the bacterial chromosome.
Origin of the Thymidine Kinase Induced by Polyoma Virus in Productively Infected Cells
Authors: Basilico Claudio , Matsuya Yutaka , Green Howard
Published: January 2020

Cells of the 3T3 mouse line efficiently supported the multiplication of polyoma virus, and the infectious process was accompanied by a marked increase in thymidine kinase (TK) activity. Two lines of 5-bromodeoxyuridine-resistant 3T3 cells have been isolated. As expected, these cells incorporated practically no exogenous thymidine into their deoxyribonucleic acid (DNA) and contained negligible TK activity. Like the parental 3T3 cells, TK
−
lines were susceptible to productive infection by polyoma virus, but infection did not lead to an increase in TK activity. Since kinase activity did appear after infection with another virus (vaccinia) known to contain the gene(s) for that enzyme, it is concluded that TK is not one of the gene products of polyoma virus. As induction of cellular DNA synthesis by polyoma virus occurs normally when the TK
−
cells are infected in the stationary phase, TK cannot play a role in the determination of this phenomenon.
Variations in Genetic Recombination Due to Amber Mutations in T4D Bacteriophage
Authors: Berger Hillard , Warren A. Jane , Fry Kirk E.
Published: January 2020

Recombination experiments were performed to assess the affect of amber mutations in 12 genes of T4D bacteriophage on genetic recombination. Crosses were performed in various suppressor-containing bacterial hosts to permit the production of progeny phage. Amber mutations in genes
32, 46
, and
47
caused decreased recombination, amber mutations in genes
30, 41, 42, 43, 56, 61
, and
62
caused increased recombination, whereas mutations in genes
63
and
37
showed no demonstrable effect on recombination.
Mycoplasmal Deoxyribonuclease Activity in Virus-infected L-Cell Cultures
Authors: Stock David A. , Gentry Glenn A.
Published: January 2020

Cell-free extracts of
Mycoplasma hominis
and medium from 72-hr broth cultures had deoxyribonuclease activity like that of deoxyribonuclease I. Mg
++
stimulated activity, and the
p
H optimum was between 8.0 and 9.0. Double-stranded or heatdenatured deoxyribonucleic acid (DNA) served as a substrate, and oligonucleotides were produced. Cell-free extracts of L cells infected with
M. hominis
or
M. hominis
plus equine abortion virus (equine herpes virus, EAV) had greatly increased activity over that of extracts of L cells or of L cells infected with EAV alone. In the absence of
M. hominis
, however, extracts had little activity, most of which was in virus-infected cell cultures. Activity was found in the culture medium only in those systems in which
M. hominis
was present. It is concluded that
M. hominis
can contribute significant deoxyribonuclease activity to virus-infected as well as virusfree cell cultures. Perhaps the most interesting question arising concerns the ability of EAV, a DNA virus, to replicate successfully despite the presence of deoxyribonuclease activity at the site of replication (the nucleus).
Characterization of Influenza Virus Ribonucleic Acid Duplex Produced by Annealing In Vitro
Authors: Nayak D. P. , Baluda M. A.
Published: January 2020

A ribonuclease-resistant ribonucleic acid (RNA) with a sedimentation coefficient of 12
S
was obtained by self-annealing influenza virus-specific RNA isolated from infected cells. It had the properties of double-stranded RNA. (i) Sedimentation behavior in sucrose gradient was independent of salt concentration. (ii) Thermal transition profile was sharp; the melting temperature is 83 C in 0.1 SSC (0.15
m
NaCl plus 0.015
m
sodium citrate) and 98 C in SSC. (iii) Buoyant density in cesium sulfate was 1.58 g/cm
3
compared to 1.64 g/cm
3
for single-stranded RNA. (iv) It gave rise to single-stranded RNA after denaturation. (v) The 12
S
RNA duplex contained both plus and minus strands of influenza virus. Labeled plus strands could be displaced by extraneous cold plus strands and extraneous
32
P-labeled plus strands could be incorporated into duplex after denaturation and reannealing.
Complement-Fixation Test for Detection of Herpes-like Viruses in Cell Cultures of Burkitt's Lymphoma
Authors: McCormick Kenneth J. , Stenback Wayne A. , Trentin John J. , Klein George , Nadkarni Jagadish S. , Nadkarni Jayshree J. , Clifford Peter
Published: January 2020

Although biopsies of Burkitt's tumors contained no detectable complement-fixing (CF) antigen or antigens, tumor cell lines contained CF antigen or antigens related to the presence of a herpes-like virus particle.
Immunofluorescence in the Study of Marek's Disease
Authors: Purchase H. G.
Published: January 2020

The indirect fluorescent-antibody (FA) test was applied to the detection of Marek's disease (MD) antigen in cell culture and antibody in the serum of birds. For the detection of antigen, sera were obtained from birds hyperimmunized with the JM strain of MD. MD antigen could be detected in the nucleus and in the cytoplasm of duck and chick embryo fibroblasts and in those of chick kidney cells infected with material known to contain the MD virus. Uninoculated cultures of chicken cells were always free of MD antigen. When chick kidney cells were infected with a stock cellular preparation of MD virus, infected cells could be detected after 24 hr with the FA test. At this time no cytopathological areas were seen by conventional light microscopy. By 7 days after infection, the same number of infected areas were detected by both methods, and the fluorescent areas coincided with the cytopathological areas. This indicates that the fluorescent areas and the areas with cytopathology are caused by the same agent. A straight-line relationship between the dilution of inoculum and the number of fluorescent or morphological foci obtained indicates that one infectious unit produced one fluorescent or morphological focus. In addition, this time sequence study confirmed the cell association of the virus and demonstrated the cell-to-cell spread of infection. Cell cultures inoculated with eight different isolates of MD were tested in all combinations with sera prepared against the same isolates. The antigens were indistinguishable from one another, indicating that either the strains are antigenically identical or there is a common antigen or contaminant in all of them so that they stained equally well. The FA test can detect MD antigen before cytopathological areas develop in cell culture; however, the small size of the area usually examined precludes its use in initial isolations in which only a small number of infectious units are present in the inoculum. MD-infected cells contain a heat-stable antigen similar to that found in herpes simplex-infected cells.
Effect of Ultraviolet Irradiation and Actinomycin D on Polyoma Virus Replication in Mouse Embryo Cell Cultures
Authors: Bowen J. M. , Hughes R. G. , Dmochowski L.
Published: January 2020

Ultraviolet irradiation and actinomycin D impair the capacity of mouse embryo (ME) cells to support the replication of polyoma virus, but not of encephalomyocarditis (EMC) virus. The loss in capacity for polyoma virus synthesis was an “all-or-none” effect and followed closely upon the loss in cellular capacity for clone formation. Cells treated with either agent produced polyoma “T” antigen, but did not synthesize polyoma structural protein. Infection of untreated ME cells with polyoma virus produced marked stimulation of both deoxyribonucleic acid (DNA) synthesis and ribonucleic acid (RNA) synthesis. ME cell cultures irradiated with ultraviolet for 30 sec at 60 μw/cm
2
or treated with actinomycin D at 0.1 μg/ml for 6 hr prior to infection were incapable of synthesizing DNA or RNA, even after infection with polyoma virus. Irradiation of cells during infection produced cessation of synthesis of both RNA and DNA. Addition of actinomycin D during infection did not inhibit DNA synthesis but abolished RNA synthesis and reduced the yield of polyoma virus to 10% of that in untreated infected cultures. Both agents lost the ability to prevent replication of a full yield of polyoma virus when administered 30 hr after infection or later. The period after which neither agent inhibited polyoma replication corresponded with the period at which maximal RNA synthesis in untreated infected cultures had subsided. It can be concluded on the basis of the data presented that the functional integrity of the mouse embryo cell genome is required for the replication of polyoma virus, but not for EMC virus. Whereas the requirement for cellular DNA-dependent RNA synthesis for polyoma virus replication has been demonstrated, the exact nature of the host-cell function remains to be elucidated.
Abortive Infection of
Bacillus subtilis
Bacteriophage PBS1 in the Presence of Actinomycin D
Authors: Pritikin William B. , Reiter Harvard
Published: January 2020

Actinomycin D caused the irreversible loss of PBS1 phage infectious centers and PBS1-mediated transductants. The loss of infectious centers occurred only within the first 4 min after the addition of phage to cells. Actinomycin did not inactivate free phage or inhibit phage adsorption. Electron micrographs indicated that phage adsorbed to cells in the presence of actinomycin ejected their deoxyribonucleic acid (DNA) normally. However, when cells were infected in the presence of actinomycin, 15 to 22% of their
32
P-labeled DNA appeared in the medium, whereas only 1.5 to 7.2% of the
32
P-labeled DNA appeared in the medium during normal infection. Neither 8-azaguanine nor chloramphenicol caused a similar loss of PBS1 infectious centers or transductants. Actinomycin also caused the loss of SP10 infectious centers but it had no effect on SP01 or φ29 infections. We conclude that actinomycin causes abortion of PBS1 infection by inhibiting the uptake or retention of phage DNA into host cells. The immunity of SP01 and φ29 infections to actinomycin probably reflects differences in the penetration mechanisms of these phages.
Genetic Analysis of
tox
+
and
tox
−
Bacteriophages of
Corynebacterium diphtheriae
Authors: Holmes Randall K. , Barksdale Lane
Published: January 2020

A series of mutants derived from the temperate corynebacteriophages β
tox+
, γ
tox−
, and L
tox+
was isolated and characterized. In three-factor crosses between mutant β phages the relative map order of the genetic markers determining extended host ranges (
h
and
h
′) and loss of ability to lysogenize (
c
) was found to be
h
--
c
--
h
′. Recombination between markers was observed in matings between phage β and the heteroimmune corynebacteriophages γ and L. In such matings between heteroimmune phages the
c
markers of phages β and γ failed to segregate from the
imm
markers which determine the specificity of lysogenic immunity in these phages. The factor which directs the synthesis of diphtherial toxin during infection of appropriate corynebacterial hosts by toxinogenic corynebacteriophages is designated
tox
+
. It was possible to show that the
tox
+
determinant of phage β behaves as a single genetic element which occupies a position between the loci
h
and
imm
on the genetic map of this phage. Genetic recombination between mutants of phage β occurred at very low frequencies in biparental matings performed by mixed infection of
Corynebacterium diphtheriae
C7
s
(−)
tox−
. Considerably higher recombination frequencies were observed when lysogenic bacterial strains carrying one parental phage as prophage were induced by ultraviolet irradiation and then superinfected by the second parental phage. Maximal stimulation of genetic recombination between mutant β phages was detected when superinfection followed ultraviolet irradiation of the lysogenic cells within a limited period of time. In matings between phages with incomplete genetic homology, the stimulation of recombination by ultraviolet radiation was much less effective.
Immunological characterization of mouse mammary tumor virus p10 and its presence in mammary tumors and sera of tumor-bearing mice
Authors: Arthur L O , Fine D L
Published: January 2020

Mouse mammary tumor virus (MMTV) p10 and gp52 were purified and used as radiolabeled antigens in sensitive radioimmunoassays. These radioimmunoassays were specific for MMTV proteins since detergent-disrupted MMTV from C3H/HeN, RIII, and GR/N mice gave complete competition, whereas C3H/HeNf liver extracts and other lysed retroviruses did not. Both gp52 and p10 are coded by the viral genome, since MMTV grown in a heterologous cell line (feline kidney cells) competed in these assays. Sera from mammary tumor-bearing mice and mammary tumors from C3H/HeN and C3H/HeNf mice competed in both the gp52 and the p10 assays. Although these radioimmunoassays detected predominantly group-specific antigenic determinants in C3H/HeN and C3H/HeNf tumor extracts, type specificity was also found with gp52. Absorption of the anti-MMTV serum with C3H/HeNf tumor extracts removed all antibodies directed against p10 and decreased the anti-gp52 titer approximately 30-fold. When this absorbed antiserum was used at limiting dilution in the gp52 radioimmunoassay, C3H/HeN tumor extracts gave complete competition, whereas no competition was found with C3H/HeNf tumor extracts.
Structural studies of retroviruses: characterization of oligomeric complexes of murine and feline leukemia virus envelope and core components formed upon cross-linking
Authors: Pinter A , Fleissner E
Published: January 2020

To examine the protein proximity and subunit organization of type C retroviruses, preparations of AKR murine leukemia virus were treated with bifunctional cross-linking reagents and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The cross-linked components obtained were characterized by immunoprecipitation with monospecific antisera against purified viral proteins, followed by SDS-PAGE analysis both before and after cleavage of the cross-links. With these procedures, complexes of both viral envelope and core components were identified. The major envelope subunit obtained was a large (apparent molecular weight of 450,000 to 500,000), glycosylated complex, composed of four to six gp70-p15(E) subunits. This complex was detected over a 100-fold range of cross-linker concentration and thus seems to represent a particularly stable viral substructure. The cross-linked complexes of the core proteins consisted of oligomers of p30 dimers, suggesting that the p30 dimer is a basic structural unit of the viral core. When virion preparations, which had previously been disrupted with the nonionic detergent Nonidet P-40, were cross-linked, the envelope complex was still observed, indicating that this structure is stable in the presence of Nonidet P-40. A similar envelope structure was observed for feline leukemia virus, suggesting that such a complex may be a conserved feature of oncornavirus structure.
Adsorption, Penetration, and Uncoating of Murine Leukemia Virus Studied by Using Its Reverse Transcriptase
Authors: Aboud Mordechai , Shoor Ruth , Salzberg Samuel
Published: January 2020

A procedure using the virus-associated reverse transcriptase was developed for following the kinetics of adsorption, penetration, and uncoating of murine leukemia virus. Viral adsorption to cell membrane was determined by assaying this enzyme activity in isolated debris of mechanically disrupted cells after infection with murine leukemia virus in the presence of actinomycin D. At 37°C, viral adsorption proceeded at a high initial rate, but after 5 min of incubation with the virus, it gradually slowed down. At 4°C, viral adsorption was slower but proceeded at a linear rate. Intracellular virus was determined by centrifuging the cytoplasmic fraction of the disrupted cells at 105,000 ×
g
for 45 min and assaying reverse-transcriptase activity in the high-speed pellet thus obtained. Sucrose gradient analysis of the enzyme activity recovered from the cytoplasm of infected cells indicated that this activity represented intact virus particles. No appreciable amount of such particles was recovered from the cytoplasm of cells infected at 4°C. This indicates that the virions recovered from the cytoplasm of cells infected at 37°C are indeed intracellular virus particles which penetrated into the cells and not just membrane-bound particles mechanically released to the cytoplasmic fraction during cell disruption. By this procedure intracellular virus was found to accumulate in the cytoplasm, reaching a maximal level within 20 min. The accumulated intracellular virus particles gradually disappeared from the cytoplasm, evidently due to their uncoating which was completed within 80 min.
Simian Virus 40 t Antigen Affects the Sensitivity of Cellular DNA Synthesis to Theophylline
Authors: Rundell Kathleen , Cox Janet
Published: January 2020

Cellular DNA synthesis induced by simian virus 40 mutants that lack t antigen is sensitive to concentrations of theophylline that do not affect wild-type-induced synthesis.
Distinctive RNA transcriptase, polyadenylic acid polymerase, and polyuridylic acid polymerase activities associated with Pichinde virus
Authors: Leung W C , Leung M F , Rawls W E
Published: January 2020

Three RNA polymerase activities were found and associated with purified Pichinde virus, a member of the Arenaviridae. A heat-labile polymerase activity which required all four ribonucleoside triphosphates for optimal activity co-sedimented on sucrose gradient centrifugation with the viral ribonucleoprotein complex from detergent-disrupted virus preparations. This enzyme synthesized heteropolymers which represented about 23% of the genome RNA as determined by nucleic acid hybridization. Two relatively heat-stable polymerase activities which differed in their cation requirement and substrate specificity were recovered with the virus-associated ribosomes. These polymerase activities synthesized homopolymers of limited chain length: in the presence of 10 mM Mg2%, polyuridylic acid was made, whereas in the presence of 1 mM Mn2%, polyadenylic acid was made. The addition of complementary RNA synthesized with the viral transcriptase in vitro to the reaction mixture containing the polyadenylic acid polymerase activity resulted in the terminal addition of polyadenylic acid to the complementary RNA. The possible function of the ribosome-associated polymerase activities in the replication of the virus is discussed.
Amino acid and sugar transport in Escherichia coli (ColIb) during abortive infection by bacteriophage T5
Authors: Glenn J , Duckworth D H
Published: January 2020

T5 bacteriophage cannot replicate in Escherichia coli containing the colicinogenic factor ColIb. We show that active transport of proline and glutamine begins to decline at about 10 min after infection, the same time at which macromolecular synthesis stops during abortive infection. Uptake of alpha-methylglucoside is stimulated, however, and this change is evident even by 5 min after infection. These changes in membrane function do not occur during infections that are productive because of mutations on the plasmid or phage. The results suggest that the abortive infection is caused by membrane depolarization.
Tryptic peptide analysis of gag and gag-pol gene products of Rauscher murine leukemia virus
Authors: Kopchick J J , Karshin W L , Arlinghaus R B
Published: January 2020

[3H]tyrosine-labeled viral precursor polyproteins and known mature viral proteins derived from the Rauscher murine leukemia virus gag and pol genes were examined by two-dimensional tryptic peptide mapping. Pr200gag-pol was found to contain peptide sequences of the viral core proteins p30, p15, p12, and p10, as well as peptide sequences found in the cell-associated reverse transcriptase. Intermediate reverse transcriptase precursor Pr125pol lacked peptide sequences of the four-core proteins but contained reverse transcriptase-specific tryptic peptides plus two additional tyrosine-containing tryptic peptides not related to gag or pol gene products. Methionine-containing tryptic peptide analysis also suggested the presence of additional protein material in Pr125pol (Kopchick et al., Proc. Natl. Acad. Sci. U.S.A. 75:2016-2020, 1978). Pr200gag-pol, although containing both viral core and reverse transcriptase-assoicated methionine and tyrosine tryptic peptides, also contained additional tryptic peptides. Thes are of two classes: (i) tryptic peptides associated with the Pr125pol but not Pr80pol and (ii) tryptic peptides not found in Pr125pol or in any known viral protein. One interpretation of these results is that Pr200gag-pol contains additional gene products aside from the gag and pol genes. Pr80gag and Pr65gag peptide maps were also examined and found to have sequences of all four core proteins. Pr65gag was found to contain two p30 tyrosine tryptic peptides that were absent in Pr80gag, suggesting that Pr80gag may not be the precursor to Pr65gag. Pr80gag, as expected from its larger size, also contained tryptic peptides not found in Pr65gag. Two of these additional Pr80gag tryptic peptides were found in Pr80pol as well but not in any of the viral core proteins, suggesting that Pr80gag and Pr80pol may have overlapping peptide sequences. Consistent with this finding is the conclusion that Pr80gag terminates within the pol gene. A model that describes the relationship of these recent findings to viral gene products is presented.
Topography of a flexible ribonucleoprotein helix: protein-protein contacts in Sendai virus nucleocapsids
Authors: Raghow R , Kingsbury D W , Portner A , George S
Published: January 2020

Contacts among the three polypeptide species in the flexible helical nucleocapsids of a paramyxovirus were examined with bifunctional protein cross-linking reagents. Polypeptides L and P, minor components of Sendai virus nucleocapsids implicated in viral RNA polymerase activity, were efficiently cross-linked into large complexes, indicating that they enjoy abundant contacts with neighboring protein molecules in the helix. Less reactivity was found in the case of the major structural polypeptide, NP; about half of all molecules of NP formed large cross-linked complexes, most of the rest remaining as monomers along with a small proportion of homodimers and low-order oligomers. Marked heterogeneity in the cross-linking reactivity of NP molecules, which may reflect the conformational quasi-equivalence inherent in a flexible helix, was indicated by the production of several conformers of homodimers and other low-order oligomers of NP, and by failure of the kinetics of NP cross-linking to conform to a simple statistical model of random polmerization. The validity of the statistical model was shown by cross-linking experiments with the rigid helical virus, tobacco mosaic virus.
Analysis of Proteins of Mouse Sarcoma Pseudotype Viruses: Type-Specific Radioimmunoassays for Ecotropic Virus p30's
Authors: Kennel Stephen J. , Tennant Raymond W.
Published: January 2020

Murine sarcoma virus pseudotypes were prepared by infection of nonproducer cells (A1-2), which were transformed by the Gazdar strain of mouse sarcoma virus, with Gross (N-tropic), WN1802B (B-tropic), or Moloney (NB-tropic) viruses. The respective host range pseudotype sarcoma viruses were defined by the titration characteristics on cells with the appropriate
Fv-1
genotype. Proteins from virus progeny were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Bands present in both the 65,000- and the 10,000- to 20,000- molecular-weight regions of the gel distinguished the pseudotype viruses from their respective helpers. Furthermore, two protein bands were noted in the p30 region of murine sarcoma virus (Gross), one corresponding to Gross virus p30, and another of slightly slower mobility. However, since the mobility of the putative sarcoma p30 is nearly indentical to that of WN1802B, its presence could not be established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Type-specific radioimmunoassays for Gross virus p30 and for WN1802B p30 were applied for analysis of pseudotype preparations, and among several ecotropic viruses tested, only the homologous virus scored in the respective assay. By use of these assays, pseudotype viruses were found to contain only 8 to 48% helper-specific p30's; the remainder is presumably derived from the sarcoma virus.
Genetics of xenotropic virus expression in mice. I. Evidence for a single locus regulating spontaneous production of infectious virus in crosses involving NZB/B1NJ and 129/J strains of mice
Authors: Levy J A , Joyner J , Nayar K T , Kouri R E
Published: January 2020

The extent of infectious xenotropic virus expression in homogenized splenic tissues from the high-virus-expressing NZB/BINJ mice and the non-virus-expressing 129/J mice and their crosses has been examined. The data suggest that a single autosomal "dominant-like" gene controls the spontaneous production and release of infectious xenotropic virus in NZB mice. Analysis of infectious virus production in second-backcross families [(F1 X 129) X 129] confirmed this conclusion. Variations in the amount of X-tropic virus released were evident in all genetic crosses. Virus titers (expressed as focus-forming units per milliliter) of supernatant fluid ranged from high levels in the NZB mice to somewhat lower levels in crosses involving the 129 mice. In the absence of a definite pattern in the titers observed in the genetic crosses studied, the term dominant-like is proposed for the single gene regulating the expression of X-tropic virus in NZB mice.
Structure of the membrane protein of influenza virus. I. Isolation and characterization of cyanogen bromide cleavage products
Authors: Robertson B H , Bhown A S , Compans R W , Bennett J C
Published: January 2020

After cleavage of the membrane (M) protein of influenza A/WSN virus by using cyanogen bromide (CNBr), six peptide peaks representing approximate molecular weights of 6,000, 4,000, 2,200, 1,600, 1,200, and 1,000 were resolved by gel filtration on BioGel P6. Analysis by thin-layer chromatography indicates that the first, second, fourth, and fifth peaks contain single-peptide components, whereas the third and sixth peaks contain more than one peptide. By using Whatman CM52 ion-exchange chromatography in 5 M urea, four peptides were resolved from the third BioGel P6 peak. The amino acid composition of each of the purified peptides has been determined, and partial sequences were obtained for several peptides. Based on finding a blocked amino terminal residue, the 6,000-dalton fragment appears to contain the amino terminus of the M protein, whereas the carboxy terminal peptide was identified as a 2,000-dalton peptide.
Physical map of bacteriophage BF23 DNA: terminal redundancy and localization of single-chain interruptions
Authors: Rhoades M , Lange-Gustafson B
Published: January 2020

The DNA of bacteriophage BF23 possesses two structural features, localized single-chain interruptions and a large terminal repetition, previously described for T5, a closely related virus. As is the case for T5, single-chain interruptions occur with variable frequencies at a small number of fixed sites within one strand of the double-stranded BF23 genome. The sites where interruptions occur with the highest frequencies were napped by an electrophoretic analysis of the single-stranded fragments produced by denaturation of BF23 DNA. The positions of these fragments were determined by degrading BF23 DNA to various extents with lambda exonuclease and observing the relative order with which they were (i) degraded or (ii) released intact from the undenatured duplex. The exact locations of the interruptions were determined from analysis of analogous duplex fragments produced by degrading exonuclease III-treated BF23 DNA with a single-strand-specific endonuclease. BF23 has five principal sites (located at 7.9, 18.7, 32.4, 65.8, and 99.6% from the left end of the DNA) where interruptions occur in most molecules. The principal interruptions in T5 DNA occur at similar positions. The locations of eight secondary interruptions in BF23 DNA were also determined. In general, BF23 DNA has fewer secondary interruptions than t5 dna, although there is at least one location where an interruption occurs with a greater frequency in BF23. The presence of a terminal repetition in BF23 DNA was demonstrated by annealing ligase-repaired molecules that had been partially digested with lambda exonuclease. If the complementary sequences at both ends of the DNA were exposed by exonuclease treatment, the duplex segment that resulted from annealing could be released by digestion with a single-strand-specific endonuclease. This segment was analyzed by agarose gel electrophoresis and found to represent 8.4% of BF23 DNA.
Isolation and localization of herpes simplex virus type 1 mRNA
Authors: Anderson K P , Stringer J R , Holland L E , Wagner E K
Published: January 2020

Herpes simplex virus (HSV) DNA bound to cellulose has been used as a reagent to isolate viral mRNA for size analysis on denaturing agarose gels. Total viral polysomal polyadenylated RNA was isolated from cells late after infection when such RNA has sequences encoded by approximately 45% of the HSV DNA. This RNA has a size range of from 1.5 to greater than or equal to 8 kilobases, with certain sizes, such as 1.7 to 1.9 kilobases, being favored. We have used the restriction endonucleases HindIII and XbaI singly and together to generate various sized fragments covering the entire HSV-1 genome. These fragments have been bound to cellulose to allow isolation of HSV-1 mRNA annealing to different regions of the viral genome. Discrete sizes of viral mRNA are associated with certain regions of the genome, but the mRNA population hybridizing to even the smallest restriction fragments is complex. We used hybridization of size-fractionated RNA to Southern blots of restriction fragments of HSV-1 DNA generated by the BglII as well as HindIII and XbaI endonucleases to confirm the preparative hybridization data and to provide some overlap data for positioning transcripts. The data of blot and preparative hybridization agreed very well and were combined to construct a preliminary transcription map of HSV-1. Such a map revealed at least two areas of the long unique region of the HSV-1 genome which annealed to a large number of HSV-1 transcripts. Furthermore, discrete-sized mRNA species larger than 5 kilobases in length were found only in the middle of the long unique region. The implications of these data are discussed.
Reovirus serotypes 1 and 3 differ in their in vitro association with microtubules
Authors: Babiss L E , Luftig R B , Weatherbee J A , Weihing R R , Ray U R , Fields B N
Published: January 2020

Utilizing negative-stain electron microscopy in which similar concentrations of reovirus types 1 and 3 are incubated with a carbon support film containing chick brain, rabbit brain, or HeLa cell microtubules, 81% of the type 1 and 56% of type 3 exhibited an association with the apparent "edge" of the microtubule. This implies that there is a high level of specific affinity for type 1 but not for type 3 to microtubules, since it has previously been determined that only 50% of randomly associated particles would be associated with the edge. The high edge binding of reovirus type 1 is virtually independent of the origin of microtubule, or of whether microtubules or virus has been initially adhered to the support film. On the other hand, reovirus type 1-specific antiserum reduced the edge binding or reovirus type 1 to 45%, whereas type 3 specific antiserum caused no less (within the variability of the assay) of the edge binding of reovirus type 1 to microtubules (76% edge bound). High edge binding of reovirus type 1 to microtubules is correlated with the presence of type 1 or sigma 1 polypeptide. This minor outer capsid polypeptide is encoded in the S1 double-stranded RNA segment and is the viral hemagglutinin and neutralization antigen. Recombinant reovirus clones containing the S1 double-stranded RNA segment of type 1 (80 and 802) show about 85% edge binding, as compared to a value of 42% for clones and the S1 gene of type 3 (204. Electron microscopy of purified reovirus types 1 and 3 by negative staining reveals that type 1 and 802 capsomers are distinctly visualized, whereas those of type 3 and 204 appear diffuse. Thus, the greater in vitro binding of type 1 to microtubules may reflect an increased accessibility of certain of its outer capsomers, and thereby, sigma 1 polypeptides to microtubules. Examination of its outer sections of reovirus type 1- and 3-infected cells at 24 to 48 h postinfection at 31 degrees C showed that about eight times as many viral factoris in type 1-infected cells exhibited an extensive association of virus particles with microtubules, as compared to viral factories of type 3-infected cells. Thus, both in vivo and in vitro there appears to be a greater specificity for the association of reovirus type 1 particles with microtubules, as compared to reovirus type 3 particles.