bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties and origins of infectious rhinovirus type 14 particles of different buoyant densities
Authors: Gauntt C J , Griffith M M , Sauck J R , Upson R H , Carlson E C
Published: January 2020

Isopycnic centrifugation of rhinovirus type 14 (RV14), purified from infected HeLa or KB cell cultures, into CsCl gradients resolved two bands of infectious virus particles with buoyant density values of 1.409 +/- 0.007 (H virus) and 1.386 +/- 0.004 (L virus) g/ml. Only H virus was detected by incorporation of radiolabeled uridine into viral RNA, and H virus accounted for the majority of infectivity in gradients. H and L virus could not be differentiated by plaque morphology, extent of neutralization by RV14-specific antiserum, or particle size. Electron microscope studies showed that most L-virus particles were associated with an amorphous material. Treatment of L virus with proteolytic enzymes or rebanding L virus in CsCl gradients resulted in recovery of the majority of infectivity as H virus. Virus purified from cell-free fluids from infected HeLa or KB cell cultures banded only as H virus. HeLa cell cultures challenged with purified H virus and harvested at 3 h postinoculation for virus purification yielded only infectious H virus. Both H and L viruses were detected in cell cultures that had been challenged with purified H virus and harvested at 12 h postinoculation. The data suggest that H virus represents progeny virus, whereas L virus represents sequestered infectious virus particles which become associated with an amorphous material and do not enter into viral replicative processes.
das Mutation in bacteriophage T4D does not suppress an amber mutation in T4 gene 59
Authors: Wiberg J S , Swanson R S
Published: January 2020

Mutations termed das were isolated originally (Hercules and Wiberg, 1971) as partial suppressors of mutants in phage T4 genes 46 and 47. Since mutants in genes 46, 47, and 59 exhibit both an early arrest of phage DNA synthesis and the loss of this arrest in the presence of chloramphenicol or of mutations of T4 genes 33 and 55, we asked whether a das mutation can also suppress a gene 59 mutant. We find that it cannot--either at the level of phage production or DNA synthesis.
Thymineless bacteriophage induction in Staphylococcus aureus. II. Specific transduction of constitutive and inducible erythromycin resistance
Authors: Lindberg M , Rudin L
Published: January 2020

Specific transduction of inducible (eroA) and constitutive (eroB) erythromycin resistance is mediated by thymineless induced lysates from derivatives of Staphylococcus aureus strain 8325(N)thy. Both loci can coexist in the same cell but segregate by transduction or transformation. The gene(s) is probably integrated in the recipient chromosome and excised at thymine starvation.
F-Factor-mediated restriction of bacteriophage T7: synthesis of RNA and protein in T7-infected Escherichia coli F- and F+ cells
Authors: Whitaker P A , Yamada Y , Nakada D
Published: January 2020

Bacteriophage T7 is unable to productively infect Escherichia coli strains carrying the sex factor F. T7 phage development, in terms of RNA and protein synthesis, was compared in T7-infected isogenic F- and F+ strains of E. coli. Slightly less T7 early mRNA and early protein were synthesized in F+ cells. In addition to the defect in T7 late protein production in F+ cells reported by others, significantly less T7 late mRNA was synthesized, about one-half of that produced in T7-infected F- cells. Moreover, host RNA synthesis was not completely inhibited. The protein-synthesizing ability of T7-infected F+ cells decayed much faster than that of F- cells both in vivo and in vitro. This faster decay appears to explain the failure of F+ cells to produce T7 late protein in vivo, even in the presence of a considerable amount of translatable T7 late mRNA. Therefore, it may not be necessary to postulate the involvement of specific translational discrimination against T7 late mRNA, although it appears that F-factor-mediated restriction of T7 involves changes in transcription as well as translation.
F-Factor-mediated restriction of bacteriophage T7: protein synthesis in cell-free systems from T7-infected Escherichia coli F- and F+ cells
Authors: Yamada Y , Nakada D
Published: January 2020

A characteristic phenomenon in the F-factor-mediated inhibition of T7 phage is a virtual absence of T7 late protein synthesis in T7-infected Escherichia coli male cells, in spite of the presence of T7 late mRNA which is translatable in vitro when isolated from the cell. To determine whether the translational defect in T7-infected F+ cells is due to a T7 late mRNA-specific translational block, or to a general decrease of F+ cell translational activity, we compared the activities of cell-free, protein-synthesizing systems prepared from isogenic F- and F+ cells harvested at different times of T7 infection. The cell-free systems from uninfected F- and F+ cells translated T7late mRNA equally as well as MS2 RNA and T7early mRNA. The activity of cell-free systems from T7-infected F+ cells to translate MS2 RAN, T7 early mRNA, and T7 late mRNA decreased concomitantly at a much faster rate than that of T7-infected F- cells. Therefore, the abortive infection of F+ cells by T7 does not result from a T7 late mRNA-specific translational inhibition, although a general reduction of the translational activity appears to be a major factor for the inability of the F+ cells to produce a sufficient amount of T7 late proteins.
Bacteriophage P22 virion protein which performs an essential early function. II. Characterization of the gene 16 function
Authors: Hoffman B , Levine M
Published: January 2020

P16 is a virion protein and, as such, is incorporated into the phage head as a step in morphogenesis. The role of P16 in assembly is not essential since particles are formed without this protein which appear normal by electron microscopy. P16 is essential when the particle infects a cell in the following cycle of infection. In the absence of functional P16, the infection does not appear to proceed beyond release of phage DNA from the capsid. No known genes are expressed, no DNA is transcribed, and the host cell survives the infection, continuing to grow and divide normally. The P16 function is required only during infection for the expression of phage functions. Induction in the absence of P16 proceeds with the expression of early and late genes and results in particle formation. P16 must be incorporated during morphogenesis into progeny particles after both infection and induction for the progeny to be infectious. The P16 function is necessary for transduction as well as for infection. Its activity is independent of new protein synthesis and it is not under immunity control. P16 can act in trans, but appears to act preferentially on the phage or phage DNA with which it is packaged. The data from complementation studies are compatible with P16 release from the capsid with the phage DNA. In the absence of P16 the infection is blocked, but the phage genome is not degraded. The various roles which have been ruled out for P16 are: (i) an early regulatory function, (ii) an enzymatic activity necessary for phage production, (iii) protection of phage DNA from host degradation enzymes, (iv) any generalized alteration of the host cell, (v) binding parental DNA to the replication complex, and (vi) any direct involvement in the replication of P22 DNA. P16 can be responsible for: (i) complete release of the DNA and disengagement from the capsid, (ii) bringing the released DNA to some necessary cell site or compartment such as the cytoplasm, (iii) removal of other virion proteins from the injected DNA, and (iv) alterations of the structure of the injected DNA.
Effect of the Fv-1 locus on the titration of murine leukemia viruses
Authors: Jolicoeur P , Baltimore D
Published: January 2020

Titration of N- and B-tropic murine leukemia viruses on sensitive and resistant cell lines has been studied by direct XC plaque assay and infective center assay. The titration of cloned B-tropic virus by infective center assay on BALB/3T3 (Fv-1b/b) and NIH/3T3 (Fv-1n/n) cells gave one-hit patterns, with 100-fold less infected NIH/3T3 cells than BALB/3T3 cells. The titration of B-tropic virus on DBA/2 cells (Fv-1n/n) was also a one-hit. The titration of a one-hit curve, and there were about 100-fold less infected BALB/3T3 cells than NIH/3T3 cells. Comparable results were obtained by titrating the cloned N-tropic virus on congenic SIM (Fv-1n/n) and SIM.R (Fv-1b/b) cells or the Gross N-tropic virus on BALB/3T3 cells. Therefore, our data indicate that the multiple-hit phenomenon described previously may not be an essential part of the Fv-1 gene restriction.
Ribonucleotide Sequence Homology Among Avian Oncornaviruses
Authors: Shoyab M. , Baluda M. A.
Published: January 2020

RNA sequence relatedness among avian RNA tumor virus genomes was analyzed by inhibition of DNA-RNA hybrid formation between
3
H-labeled 35
S
viral RNA and an excess of leukemic or normal chicken cell DNA with increasing concentrations of unlabeled 35
S
viral RNA. The avian viruses tested were Rous associated virus (RAV)-0, avian myeloblastosis virus (AMV), RAV-60, RAV-61, and B-77 sarcoma virus. Hybridization of
3
H-labeled 35
S
AMV RNA with DNA from normal chicken cells was inhibited by unlabeled 35
S
RAV-0 RNA as efficiently (100%) as by unlabeled AMV RNA. Hybridization between
3
H-labeled 35
S
AMV RNA and DNA from leukemic chicken myeloblasts induced by AMV was suppressed 100 and 68% by unlabeled 35
S
RNA from AMV and RAV-0, respectively. Hybridization between
3
H-labeled RAV-0 and leukemic chicken myeloblast DNA was inhibited 100 and 67% by unlabeled 35
S
RNA from RAV-0 and AMV, respectively. It appears therefore that the AMV and RAV-0 genomes are 67 to 70% homologous and that AMV hybridizes to RAV-0 like sequences in normal chicken DNA. Hybridization between AMV RNA and leukemic chicken DNA was inhibited 40% by RNA from RAV-60 or RAV-61 and 50% by B-77 RNA. Hybridization between RAV-0 RNA and leukemic chicken DNA was inhibited 80% by RAV-60 or RAV-61 and 70% by B-77 RNA. Hybridization between
3
H-labeled 35
S
RNA from RAV-60 or RAV-61 and leukemic chicken myeloblast DNA was reduced equally by RNA from RAV-60, RAV-61, AMV or RAV-0; this suggests that RNA from RAV-60 and RAV-61 hybridizes with virus-specific sequences in leukemic DNA which are shared by AMV, RAV-0, RAV-60, and RAV-61 RNAs. Hybridization between
3
H-labeled 35
S
RNA from RAV-61 and normal pheasant DNA was inhibited 100% by homologous viral RNA, 22 to 26% by RNA from AMV or RAV-0, and 30 to 33% by RNA from RAV-60 or B-77. Nearly complete inhibition of hybridization between RAV-0 RNA and leukemic chicken DNA by a mixture of AMV and B-77 35
S
RNAs indicates that the RNA sequences shared by B-77 virus and RAV-0 are different from the sequences shared by AMV and RAV-0. It appears that different avian RNA tumor virus genomes have from 50 to 80% homology in nucleotide sequences and that the degree of hybridization between normal chicken cell DNA and a given viral RNA can be predicted from the homology that exists between the viral RNA tested and RAV-0 RNA.
Viral RNA Synthesis and Levels of DNA-Dependent RNA Polymerases During Replication of Adenovirus 2
Authors: Weinmann R. , Jaehning J. A. , Raskas H. J. , Roeder R. G.
Published: January 2020

The rates of RNA synthesis in cultured human KB cells infected by adenovirus 2 were estimated by measuring the endogenous RNA polymerase activities in isolated nuclei. The fungal toxin α-amanitin was used to determine the relative and absolute levels of RNA synthesis by RNA polymerases I, II, and III in nuclei isolated during the course of infection. Whereas the level of endogenous RNA polymerase I activity in nuclei from infected cells remained constant relative to the level in nuclei from mock-infected cells, the endogenous RNA polymerase II and III activities each increased about 10-fold. These increases in endogenous RNA polymerase activities were accompanied by concomitant increases in the rates of synthesis in isolated nuclei of viral mRNA precursor, which was monitored by hybridization to viral DNA, and of viral 5.5
S
RNA, which was quantitated by electrophoretic analysis on polyacrylamide gels. The cellular RNA polymerase levels were measured with exogenous templates after solubilization and chromatographic resolution of the enzymes on DEAE-Sephadex, using procedures in which no losses of activity were apparent. In contrast to the endogenous RNA polymerase activities in isolated nuclei, the cellular levels of the solubilized class I, II, and III RNA polymerases remained constant throughout the course of the infection. Furthermore, no differences were detected in the chromatographic properties of the RNA polymerases obtained from infected or control mock-infected cells. These observations suggest that the increases in endogenous RNA polymerase activities in isolated nuclei are not due to variations in the cellular concentrations of the enzymes. Instead, it is likely that the increased endogenous enzyme activities result from either the large amounts of viral DNA template available as a consequence of viral replication or from functional modifications of the RNA polymerases or from a combination of these effects.
Kinetics of Cell Fusion Induced by a Syncytia-Producing Mutant of Herpes Simplex Virus Type I
Authors: Person Stanley , Knowles Robert W. , Read G. Sullivan , Warner Susan C. , Bond Vincent C.
Published: January 2020

We have isolated a number of plaque-morphology mutants from a strain of herpes simplex virus type I which, unlike the wild type, cause extensive cell fusion during a productive viral infection. After the onset of fusion, there is an exponential decrease in the number of single cells as a function of time after infection. At a multiplicity of infection (MOI) of 3.8 plaque-forming units per cell, fusion begins 5.3 h after infection with the number of single cells decreasing to 10% of the original number 10.2 h after infection. As the MOI is gradually increased from 0.4 to 8, the onset of fusion occurs earlier during infection. However, when the MOI is increased from 8 to 86, the onset of fusion does not occur any earlier. The rate of fusion is independent of the MOI for an MOI greater than 1. The rate of fusion varies linearly with initial cell density up to 3.5 × 10
4
cells/cm
2
and is independent of initial cell density at higher cell concentrations. To assay cell fusion we have developed a simple quantitative assay using a Coulter counter to measure the number of single cells as a function of time after infection. Data obtained using a Coulter counter are similar to those obtained with a microscope assay.
Comparisons of the immunological properties of two structural polypeptides of type C RNA viruses endogenous to old world monkeys
Authors: Stephenson J R , Reynolds R K , Aaronson S A
Published: January 2020

Immunologically very closely related type C RNA viruses are endogenous to the domestic cat and to an old world primate, the baboon. In the present studies, radioimmunological techniques have been developed for detection of the 15,000 and 30,000 molecular weight (MW) polypeptides of each virus. The much more pronounced type-specific antigenic determinants of the lower MW polypeptides made it possible to readily differentiate these viruses from each other as well as from a type C virus isolate from a second baboon species. Normal rhesus monkey tissues were partially purified and shown to contain a reactivity with MW and immunological properties similar to that of the baboon virus 30,000 MW polypeptide. Despite a similar degree of purification, antigenic reactivity like that of the baboon virus 15,000 MW polypeptide was undetectable even in the brodest immunological tests available for this polypeptide. The present findings indicate that the immunological properties of two structural polypeptides of closely related viruses endogenous to primate and feline species have undergone different rates of antigenic change in the course of evolution within their respective host cell genome.
Inhibition of friend murine leukemia virus production by low-ionic-strength medium
Authors: Ussery M A , Ramirez-Mitchell R , Hardesty B A
Published: January 2020

The effect of medium of low ionic strength on the release of virus from Friend leukemia cells has been studied. The release of infectious Friend leukemia virus is almost completely inhibited in medium of low ionic strength, as measured by a focus-forming assay (XC assay), by endogenous RNA-dependent DNA polymerase activity of released virus particles, and by electron microscope studies of the production of C-type particles. Friend leukemia virus-transformed proerythroblasts undergo extensive morphological changes in low-ionic-strength medium. The cells are viable in this medium, but they can no longer be stimulated with dimethyl sulfoxide to produce hemoglobin and increase virus production. Infectious virus is released between 30 and 120 min of resuspension of inhibited cells in normal medium. The rate of virus release after reversal of the inhibition is much greater than the rate of virus release during normal cell growth. The morphological changes occurring after dimethyl sulfoxide stimulation of Friend leukemia cells are compared with those resulting from resuspension in normal medium of cells inhibited by low ionic strength.
Isolation and characterization of Caulobacter crecentus bacteriophage phi Cd1
Authors: West D , Lagenaur C , Agabian N
Published: January 2020

A DNA-containing bacteriophage, phiCd1, was isolated from sewage and shown to infect both stalked and swarmer cells of Caulobacter crescentus strain CB13B1a. phiCd1 is a small, icosohedral bacteriophage, 60 nm in diameter, which possesses a short, noncontractile tail, 10 to 12 nm in length. The bacteriophage particle is composed of at least eight structural proteins. phiCd1 nucleic acid exists as a linear duplex of DNA as judged by: (i) thermal denaturation (Tm), (ii) CsCl density gradient centrifugation, and (iii) chemical analysis of its base composition. The DNA is 61% guanosine plus cytosine, has a buoyant density in CsCl of 1.721 +/- 0.001 g/cm3, and denatures sharply at 78.5 C in 0.1 SSC (standard saline citrate) buffer. The S20, w value for the DNA is 34.3 +/- 0.1S as compared with T7 DNA, indicating a molecular weight of about 29 x 10(6).
Kinetics of utilization of Sendai virus RNA and protein in the process of virion assembly
Authors: Famulari N G , Fleissner E
Published: January 2020

The synthesis of the 50S genomic RNA and strucural proteins of Sendai virus was examined with respect to their utilization in virus assembly. It was found that during a single cycle of infection, 50S RNA was synthesized before the structural proteins and that both RNA and protein were synthesized 2 to 4 h before their appearance in released virions. Pulse-chase labeling indicated that the NP and P proteins synthesized early and the M and F proteins synthesized late were preferentially incorporated into virus relative to the other viral proteins. The kinetics of incorporation of pulse-labeled NP protein suggested that it was withdrawn from a relatively large pool whereas the M protein appeared to be present in a relatively small pool in the cytoplasm. Further, it was possible to chase pulse-labeled M protein, but not NP protein, from the cell during an 8-h time period.
Early gene expression in bacteriophage T7. I. In vivo synthesis, inactivation, and translational utilization of early mRNA's
Authors: Hercules K , Jovanovich S , Sauerbrier W
Published: January 2020

In vivo decay rates for the individual T7 early mRNA species were determined. The physical half-lives, measured at 37 C, range from 1.1 min for gene 0.7 RNA to 4.5 min for gene 0.3 RNA. Physical half-lives, as observed after rifampin inhibition of RNA synthesis and polyacylamide electrophoresis of RNAs, are approximately 30% longer than functional half-lives, as observed by 14C-labeled amino acid uptake into individual T7 early proteins. The different RNA species are synthesized at grossly different rates, 0.3 RNA at four times the rate of 1.0 RNA, 0.7 RNA at twice the rate, and 1.1 and 1.3 RNAs at about the same or a slightly lower rate than 1.0 RNA. Rho-factor-mediated termination of transcription behind genes 0.3, 0.7, and perhaps behind 1.0 is inferred from these data. The in vivo translational utilization of the individual T7 early-message species was found to vary by not more than a factor of 2.
Replication process of the parvovirus H-1 V. Isolation and characterization of temperature-sensitive H-1 mutants
Authors: Rhode S L
Published: January 2020

Two temperature-sensitive mutants of the parvovirus H-1 have been isolated and characterized. These mutants are distinguishable by the immunofluorescent staining of cells infected by them and by the thermolability of their hemagglutinins. Under restrictive conditions both mutants synthesize a missense capsid protein defective in hemmaglutination. Synthesis of the viral DNA strand was shown to be diminished for both wild-type virus and these mutants at the restrictive temperature of 39.5 C, but the mutants were more defective than the wild type at the less restrictive temperature of 38 C. Replicative form DNA replication was not decreased in these mutants. It is proposed that H-1 requires one of the capsid proteins for the synthesis of the single-stranded progeny DNA.
Induction of measles virus hemagglutinin in a persistently infected, nonvirogenic line of cells (BGM/MV)
Authors: Flanagan T D , Menna J H
Published: January 2020

BGM/MV cells carry measles virus antigens and nucleocapsid-like structures in their cytoplasm. There is no infectious virus demonstrable, and measles virus-induced cell surface changes detectable by hemadsorption (HAD) are absent. Treatment of cells with actinomycin D or cycloheximide or enucleation of cells with cytochalasin B induced surface changes in that the cells became HAD positive. 6-Azauridine treatment of cells did not inhibit the induction of HAD, suggesting that RNA synthesis was not required. Cycloheximide treatment of cells induced by enucleation inhibited the development of HAD, suggesting a requirement for protein synthesis.
Complementation Between BK Human Papovavirus and a Simian Virus 40 tsA Mutant
Authors: Mason David H. , Takemoto Kenneth K.
Published: January 2020

Complementation tests between BK human papovavirus and SV40 temperature-sensitive mutants tsA58 and tsB11 were performed. Under the reported experimental conditions, BKV complemented the “early” mutant tsA58 but failed to complement the “late” mutant tsB11.
In vitro replication of cowpea mosaic virus RNA. II. Solubilization of membrane-bound replicase and the partial purification of the solubilized enzyme
Authors: Zabel P , Jongen-Neven I , Van Krammen A
Published: January 2020

A method for the solubilization of membrane-bound Cowpea mosaic virus RNA replicase has been developed by bypassing the use of detergents. Solubilization has been achieved by washing the 31,000 x g-pellet containing the bound replicase with a Mg2+-deficient buffer. This procedure had several advantages as compared to treatments with nonionic or ionic detergents: (i) the solubilized enzyme was stable at 4 C, (ii) more than 80% of the replicase could be solubilized without loss of total enzyme activity, (iii) the replicase was rather selectively released resulting in a two- to threefold increase in specific activity per se, and (iv) most of the green color from chloroplast fragments present in the crude replicase fraction remained membrane bound resulting in only slightly colored preparations of solubilized enzyme. The solubilized replicase has been further purified by DEAE-Bio Gel column chromatography. RNA synthesis directed by the DEAE-purified enzyme was template dependent and proceeded at a linear rate for at least 9 h.
Synthesis of complementary RNA containing polyadenylic acid by Sendai virions in vitro
Authors: Colonno R J , Stone H O
Published: January 2020

Sendai virus synthesized, in vitro, [32P]AMP- and [3H]AMP-labeled RNA that ranged in size from 3 to 25S with major peaks at 7S and 13S. Both labeled products were predominantly single-stranded RNA and were complementary in base sequence to 50S virion RNA. Passage of the 3 to 25S in vitro RNA transcripts through a polyuridylic acid-cellulose column revealed that only the larger (predominantly 18S) RNA transcripts contained polyadenylic acid[poly(A)] segments capable of binding to the column. After treatment with a combination of RNase A and T1, the majority of the in vitro poly(A) sedimented at 6S although the product ranged in size from 3 to 9S. Proof that the RNase-resistant material was indeed poly(A) was obtained by nearest-neighbor analysis when 95% of the radioactivity was recovered in AMP.
Recombination between temperature-sensitive and deletion mutants of reovirus
Authors: Spandidos D A , Graham A F
Published: January 2020

In standard pairwise crosses there was no detectable recombination between defective reovirus lacking the largest genomic segment and prototypes of the seven known classes of ts mutants. However, in such crosses between R2A (201) and the various prototypes frequencies of ts+ recombinants between 2.6 and 6.1% were observed, as others have found (Fields, 1971; Fields and Joklik, 1969). An infectious center assay was devised to measure recombination in this system, and it was found that all mixedly infected cells gave rise to ts+ recombinants in crosses between prototype ts mutants, but no recombination was detectable when the defective virus was crossed with three different ts mutants. The ts mutation of mutant R2A (201) was efficiently rescued when crossed with UV-inactivated wild-type virus but not when crossed with UV-inactivated defective virus. It is concluded from these various experiments that if there is any recombination between these defective reovirions and any known class of ts mutants it is too low to be measured by methods presently available. The kinetics of recombination were measured in cells mixedly infected with R2A (201) and R2B (352) mutants. At the earliest time progeny virus could be found in the cells the frequency of ts+ recombinants was 4.5%, and this frequency remained unchanged despite a subsequent 1,000-fold increase in progeny virus.
Comparative electrophoresis of the 18-22S RNAs of Newcastle disease virus
Authors: Weiss S R , Bratt M A
Published: January 2020

Between 80 and 90% of the 18-22S Newcastle disease virus intracellular RNA molecules contain poly(A) sequences. Electrophoresis of the 18S RNA in formamide-polyacrylamide gels resolves five species resolved by electrophoresis in aqueous gels. Thus, these five RNA species are probably unique size classes of RNA and not different conformations of the same RNAs. They are of sufficient size to code for the five smaller Newcastle disease virus proteins, and their combined molecular weights represent 60% of the viral genome-a value identical to that obtained by annealing 18-22S RNA with genome RNA. Formamide or heat treatment of the 22S RNA converts most of it into species with migration rates similar to those of the 18S species. Thus, the 22S RNA may not contain unique RNA species.
Host restriction of Friend Leukemia virus coat protein synthesis
Authors: Ray U , Soeiro R , Fields B N
Published: January 2020

Fv-1 gene-mediated host restriction of Friend leukemia virus replication was investigated in terms of coat protein synthesis. By using the assay of pseudotype formation with vesicular stomatitis virus. it was shown that under restricting growth conditions the availablity of leukemia virus coat protein for pseudotype formation was decreased. These studies appear to eliminate a pure assembly defect as the mechanism of Fv-1 host restriction.
Functional half-lives of bacteriophage m13 gene 5 and gene 8 messages
Authors: Lica L , Ray D S
Published: January 2020

The half-lives of the M13 gene 5 and gene 8 messages were determined by measuring the decay in the rate of synthesis of the gene 5 and gene 8 proteins after inhibition of new RNA chain initiations with rifampin. The gene 5 and gene 8 messages decay with half-lives of approximately 2.5 and 5 min, respectively. We found no evidence of a functional M13 message with a half-life as long as that reported for hybridizable mRNA.
Intracellular distribution and sedimentation properties of virus-specific RNA in two clones of BHK cells transformed by polyoma virus
Authors: Maxwell I H
Published: January 2020

The virus-specific RNA in two independently derived clones of polyoma virus-transformed hamster cells was studied by hybridizing labeled RNA, with excess purified polyoma DNA, immoblized on filters. In one clone (PyBHK1), less than 25% of the total labeled virus-specific RNA was found in the cytoplasm, irrespective of the labeling time. In the other clone (PyBHK2), it was estimated that 39% of the total virus-specific RNA was present inthe cytoplasm after labeling for 3 h. Both the proportion of radioactive label incorporated into virus-specific RNA and the sedimentation pattern of total virus-specific RNA differed markedly between PyBHK and PyBHK2. Most of the virus-specific RNA of PyBHK1 sedimented in the range 25S-35S, whereas a prominent 18S component was present in PyBHK2. Most of the cytoplasmic virus-specific RNA in both clones sedimented at 18S-19S. The sedimentation patterns of virus-specific RNA from whole cells and from washed nuclei of PyBHK1 were closely similar: it was estimated from sedimentation analysis in dimethyl sulfoxide that the molecular weight of 50% of this RNA was within the range 1.1 X10(6) to 2.9 X 10(6). These results, demonstrating the accumulation of virus-specific RNA within the nucleus in at least one virus-transformed cell line, indicate that the large virus-specific RNA previously described in the nuclei of transformed cells may not have represented precursors of virus-specific mRNA.
High-voltage electron microscope study of the release of vaccinia virus from whole cells
Authors: Stokes G V
Published: January 2020

High-voltage (1,000-kV) electron microscope examination of whole BSC-1 cells infected with vaccinia virus at different times after infection revealed the presence of increasing numbers of virions no longer confined to factories but situated along the cell periphery of monolayer cells. Stereoscopic images showed each virus enclosed within a membrane-like component of the host cell cytoplasm. Viruses within factories appeared to lack similar enclosures. Cytochalasin B, but not vinblastine, caused the enclosures to disrupt. Vaccinia viruses were observed to escape the host cell individually from the tips of microvillie and within packets of cytoplasm. Observations suggest that the intracellular movement and release of vaccinia virus utilize a host cell cytoplasmic network that involves microfilaments for stability.
Acceleration of transformation of rat embryo cells by rat type C virus
Authors: Rasheed S , Freeman A E , Gardner M B , Huebner R J
Published: January 2020

Sprague-Dawley and Fischer rat embryo cells became spontaneously transformed about 20 passages after release of endogenous ecotropic type C virus (SD-RaLV and F-RaLV). The virus-producing transformed cells showed loss of contact inhibition, increased growth rate, and tumorigenicity in vivo. Exogenous infection of other Fischer rat embryo cultures in early passage with SD-RaLV and F-RaLV markedly accelerated their rates of transformation.
Method for the isolation of bacteriphage T4 mutants that produce particles with giant capsids
Authors: Paietta J V , McDonald T L , Doermann A H
Published: January 2020

An efficient procedure is described for isolating bacteriophage T4 mutants that produce particles with giant capsids. The selective parameters of the technique rely primarily on the giants' characteristic density in cesium gradients and on their resistance to UV radiation.
Neurovirulence and induction of hydrocephalus with parental, mutant, and revertant strains of measles virus
Authors: Breschkin A M , Haspel M V , Rapp F
Published: January 2020

The relationship between neurovirulence and induction of hydrocephalus was investigated for a measles virus temperature-sensitive mutant and its revertant. The revertant regained the neurovirulence of the parental strain. At appropriate doses the parental, mutant, and revertant strains induced hydrocephalus.
Message activity of influenza viral RNA
Authors: Tekamp P , Penhoet E E
Published: January 2020

The message activity of influenza virion RNA in the wheat germ cell-free protein-synthesizing system was investigated. RNA extracted from purified virions was found to direct the synthesis of a polypeptide that had the mobility of viral nucleocapsid protein on sodium dodecyl sulfate-polyacrylamide gels. Further characterization of the protein indicated it was not the nucleocapsid protein. No other polypeptides were detected. We conclude that influenza virion RNA is inactive as a template for the synthesis of virus-specific proteins.
Characterization of simian cells tranformed by temperature-sensitive mutants of simian virus 40
Authors: Noonan C A , Brugge J S , Butel J S
Published: January 2020

Seven lines derived from primary African green monkey kidney cells, which had survived lytic infection by wild-type simian virus 40 (SV40) or temperature-sensitive mutants belonging to the A and B complementation groups, were established. These cultures synthesize SV40 tumor (T) antigen constitutively and have been passaged more than 60 times in vitro. The cells released small amounts of virus even at high passage levels but eventually became negative for the spontaneous release of virus. Virus rescued from such "nonproducer" cells by the transfection technique exhibited the growth properties of the original inoculum virus. Four of the cell lines were tested for the presence of altered growth patterns commonly associated with SV40-induced transformation. Although each of the cell lines was greater than 99% positive for T antigen, none of the cultures could be distinguished from primary or stable lines of normal simian cells on the basis of morphology, saturation density in high or low serum concentrations, colony formation on plastic or in soft agar, hexose transport, or concanavalin A agglutinability. However, the cells could be distinguished from the parental green monkey kidney cells by a prolonged life span, the presence of T antigen, a resistance to the replication of superinfecting SV40 virus or SV40 viral DNA, and, with three of the four lines, an ability to complement the growth of human adenovirus type 7. These properties were expressed independent of the temperature of incubation. These results indicate that the presence of an immunologically reactive SV40 T antigen is not sufficient to ensure induction of phenotypic transformation and suggest that a specific interaction between viral and cellular genes and/or gene products may be a necessary requirement.
Enterovirus type 70 virion and intracellular proteins
Authors: Esposito J J , Obljeski J F
Published: January 2020

The proteins of purified enterovirus type 70 grown in rhabdomyosarcoma cells and the intracellular proteins at 4 to 5 h after infection have been examined by polyacrylamide gel electrophoresis. Virions contained four proteins: P-1 (35,000, daltons) P-2 (28,000, daltons) P-3 (27,000, daltons) and P-4 (9,000 daltons). Further, addition of ZnCl2 to infected cultures inhibited virus plaque development and interfered with post-translational cleavage.
Identification of gene products required for in vitro formation of the internal peptides of bacteriophage T4
Authors: Giri J G , McCullough J E , Champe S P
Published: January 2020

In vitro formation of both bacteriophage T4 internal peptides (II and VII) from preexisting precursor protein was shown to require the product of T4 gene 21. The proteolytic factor was detectable in extracts of cells infected with certain phage mutants blocked in early steps of head assembly but could not be demonstrated in extracts of T4 wild-type infected cells. This finding suggests that the proteolytic factor is inactivated during normal phage assembly. The product of T4 gene 22 appears to be the precursor of peptide VII but not of peptide II.
Rhinovirus multistranded RNA: dependence of the replicative form on the presence of actinomycin D
Authors: Macnaughton M R , Cooper J A , Dimmock N J
Published: January 2020

The multistranded and double-stranded RNAs synthesized in HeLa cells infected with rhinovirus in the presence and in the absence of actinomycin D have been characterized by polyacrylamide gel electrophoresis and hybridization studies. The replicative form is only found in infected cells treated with actinomycin D, whereas the replicative intermediate is found in both the presence and the absence of the drug. The significance of these results is discussed.
Synthesis of type C virus particles from murine-cultured cells induced by iododeoxyuridine. V. Effect of interferon and its interaction with dexamethasone
Authors: Wu A M , Schultz A , Gallo R C
Published: January 2020

Previous studies have shown that in certain cell systems dexamethasone may enhance the production of type C viruses. Conversely, interferon has been shown to inhibit their production. Both appear to exert their influence late in the viral replication cycle rather than on the synthesis of viral-specific RNA. In this report dexamethasone and interferon have been used to study some aspects of the mechanisms involved in the synthesis of type C viruses in murine K-BALB cells following induction of virus production by iododeoxyuridine. Interferon inhibited production of xenotropic type C virus induced by iododeoxyuridine from K-BALB cells both in the absence and presence of dexamethasone, but it did not affect production of N-tropic type C virus. Exposure of the cells to interferon for longer than 12 h was required for maximum effect. Two types of inhibitory effects were observed: one diminished by dexamethasone when the steroid was added 24 h after interferon removal, and the second resistant to dexamethasone. The concentration of intracellular group-specific antigen was diminshed after interferon and increased after dexamethasone exposure. When induced cells were treated with both interferon and dexamethasone, the intracellular group-specific protein concentration was slightly increased, but virus production was reduced 10-fold compared with induced cells treated with dexamethasone alone. We conclude that interferon and dexamethasone may affect both the synthesis of viral proteins and the assembly or release of virus particles and that dexamethasone can partially nullify the inhibitory activity of interferon. The results also support previous conclusions that the regulatory mechanisms for synthesis of viral proteins and for the release of viral particles may differ and that controls for xenotropic and ecotropic virus formation may not be identical.
Detection of adenovirus type 2-induced early polypeptides using cycloheximide pretreatment to enhance viral protein synthesis
Authors: Harter M L , Shanmugam G , Wold W S , Green M
Published: January 2020

(35S) methionine-labeled polypeptides synthesized by adenovirus type 2-infected cells have been analyzed by polyacrylamide gradient gel electrophoresis and autoradiography. Cycloheximide (CH) was added to infected cultures to accumulate early viral mRNA relative to host cell mRNA. This allowed viral proteins to be synthesized in increased amounts relative to host proteins after removal of CH and pulse-labeling with (35S)methionine. During the labeling period arabinosyl cytosine was added to prevent the synthesis of late viral proteins. This procedure facilitated the detection of six early viral-induced polypeptides, designated EP1 through EP6 (early protein), with apparent molecular weights of 75,000 (75K), 42K, 21K, 18K, 15K, and 11K. Supportive data were obtained by coelectrophoresis of (35S)- and (3H)methionine-labeled polypeptides from infected and uninfected cells, respectively. Three of these early polypeptides have not been previously reported. CH pretreatment enhanced the rates of synthesis of EP4 and EP6 20- to 30-fold and enhanced that of the others approximately twofold. The maximal rates of synthesis of the virus-induced proteins varied, in a different manner, with time postinfection and CH pretreatment. Since CH pretreatment appears to increase the levels of early viral proteins, it may be a useful procedure to assist their isolation and functional characterization.
Cytomegalovirus proteins. I. Polypeptides of virions and dense bodies
Authors: Fiala M , Honess R W , Heiner D C , Heine J W , Murnane J , Wallace R , Guze L B
Published: January 2020

Cytomegalovirus virions and dense bodies were purified by sucrose velocity and equilibrium centrifugation from the medium of fibroblasts infected with the strain AD169. The final virus preparations were purified more than 228-fold with respect to cellular proteins as determined by double-isotopic labeling and at least 1,600-fold on the basis of changes in the ratio of total protein to virus particles. The protein content of purified particles approximated that found for purified preparations of other herpesviruses. Twenty polypeptides ranging from 22,000 to greater than 230,000 molecular weight were detected in purified virus preparations by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polypeptides of virions and dense bodies were allocated on the basis of analyses of preparations containing differing percentages of virions and dense bodies. Six polypeptides were represented predominantly or exclusively in virions, and four polypeptides were represented predominantly or exclusively in dense bodies, whereas the remainder appeared to be shared by both types of particles. Four polypeptides were glycosylated, and at least three of these appeared to be shared by both particles. Four polypeptides were glycosylated, and at least three of these appeared to be shared by both particle types. The protein composition of cytomegalovirus differs profoundly from that of herpes simplex virus.
Genetic studies of coliphage P1. II. Relatedness to P7
Authors: Walker D H , Walker J T
Published: January 2020

Using semiquantitative spot tests, 107 independently isolated amber mutants of P1 were shown to be rescued by a nonpermissive strain of Escherichia coli lysogenic for P7 (previously called phiamp), indicating extensive genetic relatedness between P1 and P7. The amount of rescue observed varied with mutants from different genetic linkage clusters of P1. Although these rescue tests cannot distinguish between recombination, complementation, transactivation, or combinations thereof, a major role is indicated for recombination.
Excision of viral DNA from host cell DNA after induction of simian virus 40-transformed hamster cells
Authors: Rakusanova T , Kaplan J C , Smales W P , Black P H
Published: January 2020

Simian virus 40-transformed hamster cells were induced to produce infectious virus by treatment with mitomycin C or gamma-irradiation. A portion of the simian virus-40 DNA, which is integrated into the host cell genome in uninduced cells, was recovered in a pool of relatively low-molecular-weight DNA early after induction treatment in the absence of DNA replication. The data indicte that excision of the viral genome occurs subsequent to the induction stimulus.
Avian leukosis viruses of different subgroups and types isolated after passage of Rous sarcoma virus-Rous-associated virus-0 in cells from different ring-necked pheasant embryos
Authors: Temin H M , Kassner V K
Published: January 2020

Avian leukosis viruses of subgroups A and F (RAV-A and RAV-F) arose at a low rate after passage of Rous sarcoma virus-Rous-associated virus-0, which is subgroup E, in cells from ring-necked pheasant embryos. In cells of two embryos, all of the viruses isolated after virus passage were RAV-F. However, in cells of a third embryo, both RAV-A and RAV-F were isolated. In addition, there sometimes were type-specific differences among the different isolates of RAV-A and RAV-F from the cells of single embryos. These results indicate that the RAV-A and RAV-F probably arose by recombination of viral and cellular genes, that different ring-necked pheasant embryo may have different endogenous avian leukosis virus-related nucleotide sequences, and that recombination at different sites in these endogenous sequences might give rise to type-specific differences among the RAV-A and RAV-F.
Translation of individual host mRNA's in MPC-11 cells is differentially suppressed after infection by vesicular stomatitis virus
Authors: Nuss D L , Koch G
Published: January 2020

Infection of MPC-11 mouse plasmacytoma cells by vesicular stomatitis virus results in 30 to 35% reduction in [35S]methionine incorporation into total proteins within 30 min postinfection. By 6 h postinfection, total protein synthesis is reduced by 80 to 90%. However, even by 30 min postinfection, a differential suppression of the synthesis of individual host protein is observed. The synthesis of the immunoglobin G (IgG) heavy chain (H), and, in particular, the synthesis of IgG light chain (L), is considerably more resistant to vesicular stomatitis virus-induced inhibition than is the synthesis of the non-IgG proteins as a whole; e.g., when the synthesis of non-IgG proteins was reduced by 41%, the synthesis of the H and L chains was reduced by 28 and 7%, respectively. Furthermore, these alterations in the relative synthesis of the L chain, H chain, and non-IgG are comparable to the alterations previously observed in uninfected MPC-11 cells when the overall rate of polypeptide chain initiation was selectively reduced (D.L. Nuss and G. Koch, 1976). These results are discussed in terms of the strategy of virus-directed suppression of host mRNA translation.
Defective bud formation in human cells chronically infected with subacute sclerosing panencephalitis virus
Authors: Dubois-Dalcq M , Reese T S , Murphy M , Fuccillo D
Published: January 2020

Human prostate cells chronically infected with the Mantooth strain of subacute sclerosing panencephalitis (SSPE) virus multiply normally, fuse only occasionally to form giant cells, and yet have twisted intracytoplasmic nucleocapsids. These cells are able to support replication of vesicular stomatitis virus, although they release only small amounts of SSPE virus. To determine why carrier cells do not produce virus, they were examined with techniques for surface replication, freeze-fracturing, and immunoperoxidase labeling with SSPE antibody. The surface of carrier cells, like that of productive cells, is characterized by ridges crowned with viral antigens and devoid of the intramembrane particles revealed by freeze-fracture techniques. Since surface ridges form where nucleocapsids attach to the membrane, the shape and length of ridges are indicative of the shape and length of the underlying nucleocapsid. Whereas ridges on productive cells are serpentine in shape, those on carrier cells are typically straight or hairpin shaped, and the hairpin ridges are twice as long as serpentine ridges on productive cells. Furthermore, the spacing between ridges on carrier cells is never as small as that in productive infections, so that continuous sheets of viral membrane are never formed. The majority of carrier cells lack the round viral buds observed in productive cells but have, instead, many elongated processes attached to the cell surface. Each of these processes contains one or two hairpin ridges overlying hairpin-shaped nucleocapsids. These "hairpin buds" are restricted to a single region of the carrier cell surface, whereas viral buds are distributed over the entire surface of productive cells. Thus, there are several structural defects in carrier cells that depend on the specific interaction of a certain viral strain with a certain cell type. These defects prevent the deployment of viral antigen in some regions of the cell surface, the formation of nucleocapsids of normal length, the coiling of attached nucleocapsids, and the consolidation of sheets of viral membrane into spherical buds with the nucleocapsids coiled inside. These defects may account for the failure of carrier cells to shed infectious virus.