bluuebunny/crossref_metadata_2025 huggingface dataset:
Wild mouse ecotropic murine leukemia virus infection of inbred mice: dual-tropic virus expression precedes the onset of paralysis and lymphoma
Authors: Hoffman P M , Davidson W F , Ruscetti S K , Chused T M , Morse H C
Published: January 2020

NFS/N mice inoculated at birth with an ecotropic murine leukemia virus (Cas-Br-MuLV) obtained from wild mice developed hind limb paralysis beginning at 7 weeks of age and nonthymic lymphomas beginning at more than 20 weeks of age. Studies of 1- to 7-week-old Cas-Br-M MuLV-infected mice showed the following: (i) a marked increase in nonecotropic MuLV-related antigens on spleen cells but not thymocytes beginning at 2 weeks; (ii) the appearance of dual-tropic mink cell focus-forming (MCF) MuLV-related gp70 in spleen but not thymus or brain cells at 4 weeks; and (iii) the isolation of infectious MCF MuLV from spleen cells of 7-week-old mice. A role for MCF MuLV in Cas-Br-M MuLV-induced nonthymic lymphomas is indicated by these studies, and a role for recombinant MuLV in neurological disease is considered.
Molecular cloning of the avian myelocytomatosis virus genome and recovery of infectious virus by transfection of chicken cells
Authors: Vennström B , Moscovici C , Goodman H M , Bishop J M
Published: January 2020

The avian retrovirus myelocytomatosis virus 19 (MCV) possesses an interesting diversity of oncogenic potentials, but the virus has proven difficult to study because of its inability to replicate without the assistance of a helper virus. We have therefore isolated and amplified the genome of MCV by molecular cloning in a procaryotic vector. The topography of the cloned DNA was explored by the use of restriction endonucleases and radioactive complementary DNAs representing specific domains in avian retrovirus genomes. The cloned DNA appeared to be an authentic representation of the MCV genome: the size and genetic topography of the DNA were comparable to those of MCV, and transfection of the cloned DNA into chicken cells (in company with the DNA of a suitable helper virus) gave rise to virus with the genome and transforming potentials of MCV. The availability of cloned MCV DNA should facilitate a variety of genetic and biochemical manipulations directed at elucidating the mechanism of oncogenesis by MCV.
Characterization of polyoma mutants with altered middle and large T-antigens
Authors: Magnusson G , Nilsson M G , Dilworth S M , Smolar N
Published: January 2020

The viable polyoma mutants dl1013, dl1014, and dl1015 produced shortened middle and large T-antigens. In mouse 3T3 cells, dl1013 and dl1014 grew at normal rates, and dl1015 grew at a reduced rate. dl1015 behaved phenotypically as a double mutant, with deficiencies both in the stimulation of the host cell and the replication of viral DNA. Only the former defect could be complemented by the ts-a mutant, which produced a normal middle T-antigen and a temperature-sensitive large T-antigen. This result suggests that middle T-antigen is involved in the induction of cellular DNA synthesis. Of the three mutants, dl1015 alone failed to transform rat fibroblasts to growth in semisolid medium. This defect could not be complemented by the ts-a mutant. Determination of the base sequences of the mutant DNAs showed that dl1013 and dl1014 had overlapping deletions of 21 and 9 base pairs, respectively, and that the dl1015 deletion of 30 base pairs was contiguous to the other mutations on their 3' sides. Analyses of the mutant t-antigens showed that all three mutants produced shortened middle T-antigens, whereas only dl1015 large T-antigen was detectably reduced in size.
Biochemical analysis of the p30's of N-, B-, and B leads to NB-tropic murine leukemia viruses of BALB/c origin
Authors: Schindler J , Gautsch J W , Lerner R A , Hopkins N
Published: January 2020

Previous analysis of the virion proteins of an N- and a B-tropic type C virus of BALB/c mice, of 16 N-tropic recombinants (XLPN viruses) between these viruses, and of eight NB-tropic viruses derived from the B-tropic virus suggested that among these closely related viruses N-, B-, or NB-tropism was associated with the electrophoretic mobility of p30 on sodium dodecyl sulfate-polyacrylamide gels, and thus that p30 might determine this phenotype. To obtain further evidence for the association of structural markers of p30 with N-, B-, or NB-tropism, we have analyzed the p30's of these same viruses by using two-dimensional tryptic peptide mapping and slab gel isoelectric focusing. The results of these analyses suggest that (i) a single peptide unique to the N-tropic virus p30- is present in the p30 of all N-tropic recombinants; (ii) a single peptide unique to the B virus p30 is not present in p30's of the N-tropic recombinants, and this peptide is also absent in p30's of NB-tropic viruses derived from the B-tropic virus; and (iii) p30's of NB-tropic viruses possess a new tryptic peptide not found in the p30 of their B-tropic virus progenitors, and this new peptide is not found in the p30 of the N-tropic virus of BALB/c or the XLPN viruses. These results are consistent with the possibility that p30 may determine the N-, B-, or NB-tropism of murine leukemia viruses. In addition, these studies indicate that some of the N-tropic recombinants have experienced recombination within the p30 gene.
Physical mapping of drug resistance mutations defines an active center of the herpes simplex virus DNA polymerase enzyme
Authors: Knopf K W , Kaufman E R , Crumpacker C
Published: January 2020

The genome structures of herpes simplex virus type 1 (HSV-1)/HSV-2 intertypic recombinants have been previously determined by restriction endonuclease analysis, and these recombinants and their parental strains have been employed to demonstrate that mutations within the HSV DNA polymerase locus induce an altered HSV DNA polymerase activity, exhibiting resistance to three inhibitors of DNA polymerase. The viral DNA polymerases induced by two recombinants and their parental strains were purified and shown to possess similar molecular weights (142,000 to 144,000) and similar sensitivity to compounds which distinguish viral and cellular DNA polymerases. The HSV DNA polymerases induced by the resistant recombinant and the resistant parental strain were resistant to inhibition by phosphonoacetic acid, acycloguanosine triphosphate, and the 2',3'-dideoxynucleoside triphosphates. The resistant recombinant (R6-34) induced as much acycloguanosine triphosphate as did the sensitive recombinant (R6-26), but viral DNA synthesis in infected cells and the viral DNA polymerase activity were not inhibited. The 2',3'-dideoxynucleoside-triphosphates were effective competitive inhibitors for the HSV DNA polymerase, and the Ki values for the four 2',3'-dideoxynucleoside triphosphates were determined for the four viral DNA polymerases. The polymerases of the resistant recombinant and the resistant parent possessed a much higher Ki for the 2',3'-dideoxynucleoside triphosphates and for phosphonoacetic acid than did the sensitive strains. A 1.3-kilobase-pair region of HSV-1 DNA within the HSV DNA polymerase locus contained mutations which conferred resistance to three DNA polymerase inhibitors. This region of DNA sequences encoded for an amino acid sequence of 42,000 molecular weight and defined an active center of the HSV DNA polymerase enzyme.
Characterization of intracellular and extracellular vaccinia virus variants: N1-isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine interferes with cytoplasmic virus dissemination and release
Authors: Hiller G , Eibl H , Weber K
Published: January 2020

Infectious vaccinia virus can be purified from whole cells by experimentally induced lysis (intracellular virus) or from supernatant growth medium (extracellular virus). Extracellular virus and intracellular virus differed by buoyant density (1.237 versus 1.272 g/cm3), phospholipid content and composition, and polypeptide pattern. Differences in structural polypeptides on the virus surface could be detected by lactoperoxidase-catalyzed radioiodination or Brij treatment. Characteristic of extracellular virus was an additional polypeptide, with a molecular weight of 37,000 (37K), which represented 5 to 7% of the total particle protein. Antibodies to the 37K protein detected only some of the cell-associated particles late in normal infection. Upon treatment of infected cultures with N1-isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine, a drug which prevents vaccinia virus release, no particle-associated 37K protein could be detected. In all other properties tested so far, except for a slight difference in phospholipid composition, the virus obtained in the presence of the drug resembled the normal intracellular virus. N1-Isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine prevented vesicularization of intracellular viral particles. Lack of vesicularization was accompanied by the absence of particle-associated 37K viral protein and seemed to correlate with an inhibition of virus dissemination to the cell periphery.
Construction and isolation of a transmissible retrovirus containing the src gene of Harvey murine sarcoma virus and the thymidine kinase gene of herpes simplex virus type 1
Authors: Wei C M , Gibson M , Spear P G , Scolnick E M
Published: January 2020

We constructed lambda recombinants containing the Harvey murine sarcoma virus genome and the thymidine kinase (tk) gene of herpes simplex virus type 1 linked to each other. The tk gene was located in a position downstream from both the long terminal repeat and the src gene of Harvey murine sarcoma virus. The DNAs of the lambda recombinants were used to transfect NIH3T3 mouse fibroblasts in order to obtain Harvey murine sarcoma virus DNA-induced foci of transformed cells. The transformed foci were superinfected with a helper-independent retrovirus, and new individual retrovirus were isolated from the superinfected foci. The new viruses could induce focus formation on NIH3T3 cells and could convert NIH3T3(TK-) cells into TK+ cells by carrying the herpes simplex virus type 1 tk gene into the TK- cells. From virus-infected cells, we isolated nonproducer foci on NIH3T3 cells and TK+ transformants on NIH3T3(TK-) cells containing one such new viral genome coding for the dual properties. The new retroviral sequence in the nonproducer cells could be rescued into virus particles at high titers by superinfection with a helper-independent retrovirus. A hybridization analysis indicated that the recombinant virus contained both the Harvey murine sarcoma virus src sequence and the tk gene sequence in a single RNA species approximately 4.9 kilobases long. We concluded that retroviruses can be used as true vectors for genes other than genes that lead to oncogenesis.
In vitro proteolytic cleavage of Gazdar murine sarcoma virus p65gag
Authors: Maxwell S , Arlinghaus R B
Published: January 2020

Moloney murine leukemia virus, disrupted in concentrations of 0.1 to 0.5% Nonidet P-40, catalyzed the cleavage of p65, the gag gene polyprotein of the Gazdar strain of murine sarcoma virus, into polypeptides with sizes and antigenic determinants of murine leukemia virus-specified p30, p15, pp12, and p10. Cleavage performed in the presence of 0.15% Nonidet P-40 in water yielded polypeptides of approximately 40,000 (P40) and 25,000 (P25) Mr. In vitro cleavage performed in a buffered solution containing dithiothreitol in addition to 0.1% Nonidet P-40 allowed the efficient processing of P40 to p30 and a band migrating with p10. Immunoprecipitation with monospecific sera indicated that P40 contained p30 and p10, whereas P25 contained p15 and pp12 determinants. P40 and P25 are similar in size and antigenic properties to Pr40gag and Pr25gag observed in infected cells (Naso et al, J. Virol. 32:187-198, 1979).
Genome analysis of MG virus, a human papovavirus
Authors: Pater M M , Pater A , di Mayorca G
Published: January 2020

The genome of MG virus, a variant of the human papovavirus BK virus, consists of two molecules, M1 and M2, M1 and M2 have deletions which correspond to 0.33 to 0.55 map unit and 0.77 to 0.85 map unit, respectively, from the EcoRI site on the BK virus genome. Restriction enzyme analysis of the DNAs of these viruses revealed many alterations in both DNA species. Both M1 and M2 DNAs have three recognition sites for EcoRI. M1 has a single recognition site for HindIII and five sites for PvuII. M2 has a single recognition site for PuvII and three sites for HindIII. The sites of these and several other restriction enzymes on each DNA molecule were mapped after the cloning of M1 and M2 DNAs into pBR322 at their unique HindIII and PvuII sites, respectively.
Construction of a Genetic Map of the Baculovirus
Autographa californica
Nuclear Polyhedrosis Virus by Marker Rescue of Temperature-Sensitive Mutants
Authors: Miller Lois K.
Published: January 2020

Mutations of seven temperature-sensitive mutants of the baculovirus
Autographa californica
nuclear polyhedrosis virus (NPV) were mapped with respect to the physical restriction map of the
A. californica
NPV DNA by marker rescue. DNAs from two distantly related NPVs of the multiply embedded type and two NPVs of the singly embedded type were unable to rescue two
A. californica
NPV mutants.
Adenovirus type 5 virions can be assembled in vivo in the absence of detectable polypeptide IX
Authors: Colby W W , Shenk T
Published: January 2020

Mutant dl313 is an adenovirus type 5 deletion mutant which lacks 2,307 base pairs, including the 5' portion of the polypeptide IX gene. Mutant virions did not contain detectable levels of this polypeptide. They were substantially more thermolabile than wild-type particles and did not produce hexon nonomers upon pyridine disruption.
Thermodynamic Treatment of Bacteriophage T4B Adsorption Kinetics
Authors: Gamow Rustem I.
Published: January 2020

The activation energy was measured for the reaction of inactive phage becoming active in the presence and in the absence of
l
-tryptophan and was found to be about 50% lower in the former case.
L-Cell Virion Ribonucleic Acid
Authors: Faras A. J. , Erikson R. L.
Published: January 2020

“L-cell virion,” obtained from chronically infected 929 L-cell lines, was purified on 70% sucrose pads and its ribonucleic acid (RNA) was extracted and analyzed on sucrose gradients. Two RNA components were isolated from the virion, a rapidly sedimenting species (82
S
) and a more slowly sedimenting species (6
S
). When the fast-moving component was heated to 45 C, it yielded a homogeneous peak which now sedimented at approximately 72
S
. Upon heating to 70 C, the peak dissociates into a smaller homogeneous RNA species with a sedimentation coefficient of approximately 33
S
. Ribonuclease treatment and base composition analysis revealed that the fast-moving species is a single-stranded molecule. Base ratio analysis also revealed that the small (6
S
) RNA component is similar in its base composition to L-cell ribosomal RNA and distinctly different from the base composition of the large (72
S
) RNA component. Actinomycin D inhibits production of the L-cell virion by the L-cell line.
Abortive Infection of
Shigella dysenteriae
P2 by T2 Bacteriophage
Authors: Smith Helene S. , Pizer Lewis I. , Pylkas Laird , Lederberg Seymour
Published: January 2020

We have investigated some of the biochemical events that accompany the abortive infection by T2 of
Shigella dysenteriae
lysogenized with the temperate phage P2. After infection with T2, protein and RNA synthesis continued for 3 to 5 min. The virus-induced enzyme, deoxycytidylate hydroxymethylase was produced in reduced amounts (15% of normal), and the extent of deoxyribonucleic acid (DNA) synthesis was 0.1% of that found with a nonlysogenic strain. Measurements of the production of acid-soluble fragments and sedimentation analyses failed to detect enzymatic degradation of the infecting viral DNA which could be specifically related to the presence of the prophage P2. Each interaction between T2 and a bacterium resulted in the death of the cell. This observation is consistent with results obtained with other types of bacteria which show that only when a nucleolytic attack occurs on T2 DNA does the cell have an increased capacity to survive after adsorption of T2.
Rescue of Simian Virus 40 from Cell Lines Transformed at High and at Low Input Multiplicities by Unirradiated or Ultraviolet-irradiated Virus
Authors: Kit Saul , Brown McKay
Published: January 2020

The relation between simian virus 40 (SV40) input multiplicity during transformation of primary mouse kidney cultures and the subsequent rescue of SV40 from clonal lines of transformed cells has been studied. Primary mouse kidney cultures were transformed with unirradiated SV40 at input multiplicities varying from 0.06 to 200 plaque-forming units (PFU) /cell or with SV40 irradiated with ultraviolet (UV) light to a survival of 0.04 to 0.01. All of the transformed lines contained the intranuclear SV40 T antigen, but cell-free extracts prepared from the transformed cell lines failed to yield infectious virus when assayed on monkey kidney cell (CV-1) monolayers. After fusion with susceptible CV-1 cells induced by UV-inactivated Sendai, all of the lines transformed by unirradiated virus yielded infectious SV40. The frequency of induction and the incidence of successful trials did not depend on the multiplicity of infection. “Good” yielders were obtained from mouse kidney cells transformed at the low input multiplicity of 0.06 PFU /cell. In contrast, only 4 of 12 clonal lines transformed at moderately low input multiplicity, and none of the lines transformed at very low input multiplicity with UV-irradiated virus yielded infectious SV40. The four positive lines have been classified as “poor” or “rare” yielders.
Early Events of Virus-Cell Interaction in an Adenovirus System
Authors: Lonberg-Holm Karl , Philipson Lennart
Published: January 2020

The interaction of
32
P-labeled adenovirus type 2 and HeLa or KB cells has been examined during early infection. The kinetics of virus uncoating to deoxyribonuclease-sensitive products, the partial characterization of three such products by gradient centrifugation, and the distribution of these products in the extranuclear and nuclear portions of infected cells are reported. The results are compatible with the following model. Extracellular virus attaches to a receptor on the plasma membrane. The membrane-bound virus has a half-life of less than 15 min and is transformed to a partly uncoated product which is free inside the cell and about half of which rapidly enters the cell nucleus. This is rapidly transformed, in both cytoplasm and nucleus, to a membrane-bound virion “core.” The proteins of the bound “core” are then removed from the intact virus deoxyribonucleic acid (DNA). In the nucleus, viral DNA is the main product and there the overall sequence is completed in about 2 hr.
Host-Virus Interaction in Ribonucleic Acid Bacteriophage-Infected
Escherichia coli
Authors: Haywood Anne M. , Cramer Jane Harris , Shoemaker Nadja Lancaster
Published: January 2020

When actinomycin-treated, MS2-infected
Escherichia coli
are labeled during a brief period later than 16 min after infection, the newly synthesized MS2 ribonucleic acid (RNA) appears first in the 30,000 ×
g
sediment, probably bound to fragments of bacterial membranes, since the radioactivity can be released from the sediment with deoxycholate or urea. With longer labeling times, radioactivity also appears in the 30,000 ×
g
supernatant fluid. While on the membrane, the RNA is organized into particles with sedimentation coefficients of 40, 32, and 27
S
in the presence of low Mg
2+
. In the presence of high Mg
+
, MS2-specific RNA is found in polyribosomes. These data are interpreted to mean that MS2-specific RNA is synthesized and organized into larger structures on membrane. More than 8 min of labeling is required before radioactivity is found in the 81
S
virion which appears in the supernatant fluid.
Replication of Canine Herpesvirus
Authors: Strandberg John D. , Aurelian Laure
Published: January 2020

The studies reported in this paper demonstrate that, although canine herpesvirus differs from other herpesviruses in that it is characterized by a restricted host range, the pattern of virus development in the permissive host closely resembles that previously described for herpes simplex virus. These experiments also reveal the formation in the infected dog kidney cells of a system of tubules and channels in which virions accumulate. It is suggested that these membrane-bound structures serve to protect enveloped virus from being uncoated in the cytoplasm and function in virus release from the infected cells.
Anomalous Induction of Mycobacteriophages Mediated by Mitomycin C
Authors: Rieber Manuel , Imaeda Tamotsu
Published: January 2020

Mitomycin C has been found to stimulate the production of long-tailed defective bacteriophages and poly tails in thick cell wall mycobacterial mutants.
Simian Virus 40-Induced T and Tumor Antigens
Authors: Potter C. W. , Mclaughlin Bridget C. , Oxford J. S.
Published: January 2020

Antigen extracts from simian virus 40 (SV40) transplanted hamster tumors were studied by rate-zonal centrifugation. Three species or molecular forms of antigen were demonstrated. The major antigen component corresponded to a molecular weight of 65,000 to 75,000, and two larger species were detectable in smaller quantities. Similar studies were carried out on SV40 virus-induced T antigen from BSC-1 cells. Three antigen components were again detected. Quantitative differences in the expression of “T” and tumor antigen species were reproducibly found.
Proteins of the Group B Arbovirus Kunjin
Authors: Westaway E. G. , Reedman Beverley M.
Published: January 2020

Purified Kunjin virus was disrupted with sodium dodecyl sulfate, urea, and mercaptoethanol or acetic acid. Electrophoresis on 7.5% polyacrylamide gel separated four proteins of high (120,000), intermediate (65,000) and low (18,000 and 13,000) molecular weights. A “core” particle was obtained by degradation of the virion with deoxycholate at 0 C; it contained the viral ribonucleic acid and the two small structural proteins. The “envelope” material released from around the core was identified with the most prominent (intermediate) protein seen in electropherograms of virion proteins. In addition to the structural proteins, at least three additional proteins (specified by virus infection) were found in the cytoplasm. The cytoplasmic proteins associated with Kunjin virus differed in their electrophoretic profile from those associated with infection by the related Murray Valley encephalitis virus.
Polynucleotide Ligase Activity in Cells Infected with Simian Virus 40, Polyoma Virus, or Vaccinia Virus
Authors: Sambrook J. , Shatkin A. J.
Published: January 2020

The conversion of simian virus 40 (SV40) component II deoxyribonucleic acid to component I has been used to assay polynucleotide ligase in extracts of tissue culture cells. All cell types examined, including chicken, hamster, mouse, monkey, and human cells, contained adenosine triphosphate-dependent ligase. After infection of mouse embryo, monkey kidney, and HeLa cells with polyoma virus, SV40, and vaccinia virus, respectively, the enzyme activity increased, but its cofactor requirement was unchanged. In vaccinia virus-infected cells, the increased activity was localized in the cytoplasm. Ligase induction occurred in the presence of cytosine arabinoside but was prevented by puromycin. Rifampicin blocked the production of infectious vaccinia particles but had little effect on the induction of ligase.
New Bacteriophage of
Haemophilus influenzae
Authors: Samuels Janis , Clarke J. K.
Published: January 2020

Some properties of a newly isolated
Haemophilus influenzae
bacteriophage are described. The phage is morphologically distinct from previously described
H. influenzae
phages.
Electrophoresis of Adenovirus-Specified Thymidine Kinase
Authors: Hatanaka Masakazu , Twiddy Edda , Gilden Raymond
Published: January 2020

Stimulation of thymidine kinase (TK) activity occurs after abortive or productive infection with human adenoviruses. Striking changes in TK electrophoretic profile accompany this stimulation.
Defective Bacteriophage PBSH in
Bacillus subtilis
Authors: Haas Martin , Yoshikawa Hiroshi
Published: January 2020

The
adenine-16 (ade-16)
marker (the marker nearest the chromosomal origin of
Bacillus subtilis
) in purified PBSH deoxyribonucleic acid (DNA) renatured more rapidly and to a greater extent than any other marker in the phage DNA, and more rapidly and to a greater extent than all markers, including
ade-16
, in bacterial DNA. The renaturation of the phage DNA
ade-16
marker followed a first-order reaction, whereas renaturation of bacterial markers was initially a second-order reaction. No cross-linkages were detected in DNA molecules containing the
ade-16
marker. Buoyant density measurements and inactivation by heat and micrococcal deoxyribonuclease of the
ade-16
marker did not reveal large segments of clusters of the individual bases in these molecules. Alternative mechanisms for the unique renaturation behavior of the
ade-16
marker are discussed.
Effect of Cell Physiological State on Infection by Rat Virus
Authors: Tennant Raymond W. , Layman Kenneth R. , Hand Russell E.
Published: January 2020

Infection by rat virus has been studied in cultures of rat embryo cells to evaluate the Margolis-Kilham hypothesis that the virus preferentially infects tissues with actively dividing cells. An enhancement of infection was seen in cultures infected 10 hr after fresh medium was added as compared to infection of stationary cultures (infected before addition of fresh medium). Since addition of fresh medium stimulates deoxyribonucleic acid (DNA) synthesis, the number of cells per culture synthesizing DNA at the time of infection was compared with the proportion of cells which synthesized viral protein. Cells were infected before the medium change and 10 or 24 hr after the medium change and were pulse-labeled with
3
H-thymidine at the time virus was added. The cells were allowed to initiate viral protein synthesis before they were fixed and stained with fluorescein-conjugated anti-rat virus serum. Fluorescence microscopy permitted both labels to be counted simultaneouly and showed that the greatest proportion of cells synthesizing viral protein were those which had incorporated
3
H-thymidine at the time of infection.
Viral gene expression in polyoma virus-transformed rat cells and their cured revertants
Authors: Fenton R G , Basilico C
Published: January 2020

We have studied transcription of integrated viral DNA sequences in a variety of ts-a polyoma virus-transformed rat cells and cured revertants (which had undergone excision of variables amounts of integrated viral DNA) to characterize the structure of viral mRNA's produced in these lines under conditions in which integrated DNA is stable. Our results indicate that cells containing intact early region sequences, either in single-copy or tandem insertions, produce mRNA's indistinguishable from those observed early in lytic infections; sequences complementary to the polyoma late region were not transcribed from integrated viral DNA. Cured revertants no longer encoded full-length early mRNA's , but produced viral transcripts whose 3' ends mapped at an alternative early region polyadenylic acid attachment site at 99 map units or extended in to flanking host sequences. The phenotype of these revertant cells correlated with the abundance of these transcripts, suggesting that the transforming function(s) of polyoma virus controls the cellular phenotype in a dose-dependent manner. Unexpected results were obtained from studies of cells containing tandem repeats of defective viral DNA in which the polyadenylic acid attachment signal at 25.8 map units and surrounding sequences were deleted. In these cases, polyadenylated mRNA's were observed that contained sequences complementary to the early strand of the polyoma late region. These mRNA's (some larger than 8 kilobases) originated at the viral early promoter, extended into the late region, and continued into the early region of the contiguous repeat in the tandem. The multimeric mRNA's produced contained defective early regions in tandem with late region sequences. S1 analysis indicated that whereas the 5' early region sequences of readthrough transcripts were spliced in the usual manner, internal early region repeats were either unspliced or used only one of the small early region splices. When deletions in the viral readthrough transcripts were observed. This suggests that sequences nearby the AAUAAA sequence at 26 map units may control transcription termination of the polyoma early region.
Intramolecular integration within Moloney murine leukemia virus DNA
Authors: Shoemaker C , Hoffman J , Goff S P , Baltimore D
Published: January 2020

By screening a library of unintegrated, circular Moloney murine leukemia virus (M-MuLV) DNA cloned in lambda phage, we found that approximately 20% of the M-MuLV DNA inserts contained internal sequence deletions or inversions. Restriction enzyme mapping demonstrated tht the deleted segments frequently abutted a long terminal repeat (LTR) sequence, whereas the inverted segments were usually flanked by LTR sequences, suggesting that many of the variants arose as a consequence of M-MuLV DNA molecules integrating within their own DNA. Nucleotide sequencing also suggested that most of the variant inserts were generated by autointegration. One of the recombinant M-MuLV DNA inserts contained a large inverted repeat of a unique M-MuLV sequence abutting an LTR. This molecule was shown by nucleotide sequencing to have arisen by an M-MuLV DNA Molecule integrating within a second M-MuLV DNA molecule before cloning. The autointegrated M-MuLV DNA had generally lost two base pairs from the LTR sequence at each junction with target site DNA, whereas a four-base-pair direct repeat of target site DNA flanked the integrated viral DNA. Nucleotide sequencing of preintegration target site DNA showed that this four-base-pair direct repeat was present only once before integration and was thus reiterated by the integration event. The results obtained from the autointegrated clones were supported by nucleotide sequencing of the host-virus junction of two cloned M-MuLV integrated proviruses obtained from infected rat cells. Detailed analysis of the different unique target site sequences revealed no obvious common features.
Simian virus 40 early mRNA's contain multiple 5' termini upstream and downstream from a Hogness-Goldberg sequence; a shift in 5' termini during the lytic cycle is mediated by large T antigen
Authors: Ghosh P K , Lebowitz P
Published: January 2020

We have used primer-directed synthesis, separation, and sequencing of cDNA's to identify and localize the 5' termini of simian virus 40 early mRNA's. We have examined polyadenylated RNAs obtained from whole cytoplasm and polysomes of two transformed lines and from the cytoplasm of infected cells early and late in the lytic cycle, and we have attempted to correlate the results of our cDNA analyses with recent analyses of early cap structures. We have found that early mRNA's from transformed cells have three principal 5' termini, at residues 5,150, 5,154, and 5,155, with terminal transcribed sequences of CU, GC, and GG, respectively. These termini lie 21 to 26 nucleotides downstream from the early Hogness-Goldberg sequence. Transformed cell early mRNA's also contain a series of less abundant 5' termini that are copied from DNA sequences as far as 80 nucleotides downstream and a minimum of 70 to 75 nucleotides upstream from the Hogness-Goldberg sequence. The templates for the upstream 5' termini and the late simian virus 40 mRNA's overlap by a minimum of 60 to 65 nucleotides. Early mRNA's isolated from cells early in infection contain the same three principal 5' termini and downstream minor 5' termini as transformed cell mRNA's, but they lack 5' termini upstream from the Hogness-Goldberg sequence. With the onset of the late lytic phase, there is a progressive decreases in the utilization of the three principal 5' termini and additional downstream 5' termini and a progressive increase in the utilization of four major termini at residues 5,190 to 5,194, which are 10 to 15 nucleotides upstream from the Hogness-Goldberg sequence. With the onset of the late lytic phase, there is a progressive decrease in the utilization of the three principal 5' termini and additional downstream 5' termini and a progressive increase in the utilization of four major termini at residues 5,190 to 5,194, which are 10 to 15 nucleotides upstream from the Hogness-Goldberg sequence. This shift is evident in cells infected with a tsA mutant at the permissive temperature, but is aborted by growth at or shift-up to a restrictive temperature. Thus, this shift is mediated by the gene A product, large T antigen. We present two models, which are mutually exclusive, to account for the role of T antigen in the early-late shift. One involves transcription late in infection on a new DNA template synthesized during DNA replication. The second involves inhibition of initiation of early transcription at residues 5,150 to 5,155 and other downstream sites and a shift of transcription initiation principally to the upstream sites as a result of the binding of T antigen to two sites on simian virus 40 DNA downstream from the Hogness-Goldberg sequence.
Genetic structure, transforming sequence, and gene product of avian sarcoma virus UR1
Authors: Wang L H , Feldman R , Shibuya M , Hanafusa H , Notter M F , Balduzzi P C
Published: January 2020

We analyzed the genetic structure and gene products of the newly isolated avian sarcoma virus UR1, which recently has been shown to be replication defective and to contain no sequences homologous to the src gene of Rous sarcoma virus. The sizes of the genomic RNAs of UR1 and its associated helper virus, UR1AV, were determined to be 29S and 35S (5.9 and 8.5 kilobases), respectively, by gel electrophoresis and sucrose gradient sedimentation. RNase T1 oligonucleotide mapping of purified viral RNAs indicated that UR1 RNA contains eight unique oligonucleotides in the middle of the genome and shares four 5'-terminal and three 3'-terminal oligonucleotides with UR1AV RNA. The unique sequences of UR1 and Fujinami sarcoma virus were found to be closely related to each other by molecular hybridization of UR1 RNA with DNA complementary to the unique sequence of Fujinami sarcoma virus RNA, but minor differences were found by oligonucleotides fingerprinting. In the regions flanking the unique sequences, UR1 and Fujinami sarcoma viral RNAs contain distinct oligonucleotides, which are shared with oligonucleotides of the respective helper viral RNAs. Cell transformed with UR1 produce a single 29S RNA species which contains a UR1 unique sequence; this species is most likely the mRNA coding for the transforming protein. In UR1-transformed cells, a phosphoprotein fo 150,000 daltons (p150) was detected by immunoprecipitation with antiserum against gag proteins. p150 was associated with a protein kinase activity that was capable of phosphorylating p150 itself, immunoglobulin G of antiserum, and a soluble substrate, alpha-casein. This enzyme transferred phosphate exclusively to tyrosine residues of substrates in vitro, but p 150 labeled in vivo with 32P contained both phosphoserine and phosphotyrosine. The in vitro kinase reaction was not affected by the presence of cyclic AMP or cyclic GMP and strongly preferred Mn2+ over Mg2+. Thus, the properties of UR1 protein are almost identical to those of Fujinami sarcoma virus protein.
Control of expression of the vaccinia virus thymidine kinase gene
Authors: Hruby D E , Ball L A
Published: January 2020

mRNA extracted from vaccinia virus-infected cells early after infection directs cell-free synthesis of enzymatically active viral thymidine kinase (Hruby and Ball, Virology, in press). We used this assay for a specific vaccinia virus mRNA to study the induction and repression of the viral thymidine kinase gene during infection of thymidine kinase-deficient L-cells. As observed previously by other workers, the synthesis of thymidine kinase occurred immediately after infection but was switched off after 4 h later. We observed similar kinetics of accumulation and shutoff under conditions where viral DNA synthesis and late gene expression were inhibited. Cell-free translation of mRNA from infected cells showed that the concentration of functional message for viral thymidine kinase reached a peak 3 to 4 h after infection and then decreased with a half-life of about 1 h. These kinetics indicated that significant levels of thymidine kinase mRNA persisted in cells which had stopped synthesizing the enzyme. Under conditions where late gene expression was inhibited, high concentrations of functional mRNA could be isolated from cells at late times after infection. On the basis of these results, we conclude that the repression of thymidine kinase expression is mediated at the translational level by one or more early or delayed early viral genes. Repression is accompanied by, but does not depend on, the inactivation or degradation of thymidine kinase mRNA, which is a late gene function.
Early RNA of adenovirus type 3 in permissive and abortive infections
Authors: Groff D E , Daniell E
Published: January 2020

Early adenovirus type 3 cytoplasmic polyadenylated RNAs from HeLa and BHK-21 cells were detected and mapped on the viral genome by gel blotting and hybridization techniques. The sizes and locations of the 16 adenovirus type 3 RNAs were identical in the two cell types, although relative molarities of the various RNA species differed. Each of the early adenovirus type 3 RNAs was associated with polysomes in both cell types, suggesting that the abortive infection of hamster cells does not result from a defect in early adenovirus type 3 mRNA biosynthesis. No RNAs from regions transcribed late in infection of permissive cells were detected in BHK-21 cells.
Structure and phosphorylation of the Fujinami sarcoma virus gene product
Authors: Pawson T , Kung T H , Martin G S
Published: January 2020

The Fujinami avian sarcoma virus (FSV) transforming gene product, P140, is a fusion protein which contains both gag-related and FSV-specific methionine-containing tryptic peptides. The virion protease p15 cleaved p140 into two fragments: an N-terminal 33K fragment which contained all but one of the gag-related tryptic peptides and a C-terminal 120K fragment which contained all of the FSV-specific tryptic peptides. The 33K gag-related fragment from P140 phosphorylated in FSV-transformed cells contained only phosphoserine, whereas the 120K C-terminal FSV-specific fragments contained both phosphoserine and phosphotyrosine. P140 isolated from cells infected at the nonpermissive temperature with an isolate of FSV which is temperature sensitive for transformation had a normally phosphorylated 33K fragment, but a hypophosphorylated 120K fragment deficient in both phosphotyrosine and phosphoserine. When P140 was immunoprecipitated from cells and phosphorylated in vitro at tyrosine residues in the immune complex kinase reaction, only the FSV-specific fragment was labeled. These data define the structure of FSV P140 and locate the phosphorylated amino acids within the two regions of the polypeptide.
Dexamethasone Induction of the Intracellular RNAs of Mouse Mammary Tumor Virus
Authors: Robertson Donald L. , Varmus Harold E.
Published: January 2020

We have studied the kinetics of dexamethasone induction of mouse mammary tumor virus (MMTV) RNAs and proteins in virus-infected rat XC cells and GR mouse mammary tumor cells. A detectable increase in viral RNA in infected XC cells was present within 10 min after hormone addition, and half-maximal induction was achieved in less than 2 h. The increase in viral RNA concentration was apparent first in nuclear RNA and later in the cytoplasm. Within the first 15 min of induction, only genome-sized RNA (35S, 7.8 kilobases) was present in augmented amounts, whereas the major subgenomic RNA (24S, 3.8 kilobases) did not appear until at least 30 to 60 min postinduction. The sequential appearance of these RNAs, the probable mRNA's for the
gag
and
env
proteins, paralleled the order of appearance of the
gag
and
env
proteins, respectively, after hormone treatment. An additional species of viral RNA (20S, 2.5 kilobases) was detected during these induction experiments, but the role of this RNA is not known. Both subgenomic RNAs contain sequences derived from both the 5′ and 3′ termini of genomic RNA and are presumably spliced. After dexamethasone induction of infected XC cells, we detected two smaller
env
-related proteins which were not found in full hormone induction. The functional role of these smaller proteins is not known. A previously reported smaller species of RNA (13S, 1.0 kilobase) did not appear to be induced and was shown to be cellular rather than viral in origin. In the fully induced infected XC and GR mammary tumor cells, the only viral RNAs present were the 35S and 24S RNAs. In addition, mammary tumors contained only these two viral RNAs. Thus, tumor cells appear to contain only the viral RNAs which direct the synthesis of the
gag, pol
, and
env
proteins of the virion.
Host Susceptibility to endogenous viruses: defective, glycoprotein-expressing proviruses interfere with infections
Authors: Robinson H L , Astrin S M , Senior A M , Salazar F H
Published: January 2020

Three defective endogenous avian leukosis viruses, ev3, ev6 and ev9, interfered with subgroup E virus infections, ev3, ev6, and ev9 expressed high levels of subgroup E envelope glycoproteins. These glycoproteins reduced the activity of cellular receptors for subgroup E viruses. ev3 and ev6 protected chickens and cultured cells from subgroup E virus infections.
Bacteriophage T4 alc gene product: general inhibitor of transcription from cytosine-containing DNA
Authors: Kutter E M , Bradley D , Schenck R , Guttman B S , Laiken R
Published: January 2020

The alc gene of bacteriophage T4 was originally defined on the basis of mutations which allow late protein synthesis directed by T4 DNA containing cytosine rather than hydroxymethylcytosine. The question remained whether the normal alc gene product (gpalc) also blocks the transcription of early genes from cytosine-containing DNA. Complementation experiments were performed between hydroxymethylcytosine-containing phage which direct gpalc synthesis but carry mutations in a given gene(s) and cytosine-containing phage carrying that gene(s). The required protein would then have to be directed by the cytosine-containing DNA: it is looked for directly on polyacrylamide gels or through its physiological effects or both. For all early proteins examined in this way, no synthesis was observed when 95 to 100% of the hydroxymethylcytosine was substituted by cytosine in the infecting DNA, whereas there was significant synthesis with 75% substitution or less. The results indicate that gpalc is carried in with the infecting DNA or is made very early to block transcription of all cytosine-containing DNA.
Genetic recombination of bacteriophage T7 in vivo studied by use of a simple physical assay
Authors: Lee D , Sadowski P D
Published: January 2020

A new physical method was developed to assay genetic recombination of phage T7 in vivo. The assay utilized T7 mutants that carry unique restriction sites and was based on the detection of a new restriction fragment generated by recombination. Using this assay, we reexamined the genetic requirements for recombination of T7 DNA. Our results were in total agreement with previous findings in that recombination required the products of genes 3 (endonuclease), 4 (primase), 5 (DNA polymerase), and 6 (exonuclease). Recombination was found to be independent of DNA ligase and DNA packaging and maturation functions.
Characterization of a 70S polyuridylic acid polymerase isolated from foot-and-mouth disease virus-infected cells
Authors: Polatnick J , Wool S
Published: January 2020

A polyuridylic acid polymerase complex isolated from foot-and-mouth disease virus-infected cells sedimented at 70S in a sucrose gradient and appeared in the exclusion volume of an agarose column whose molecular weight cutoff was 5 x 10(6). Phenol extraction of the complex yielded a heterogeneous band of virus-specific RNA and an apparently host cell-derived 4.5 to 5S RNA, both of which are essentially single stranded. Neither RNA served as a template in the cell-free enzyme reaction. Polyacrylamide gel analysis revealed five polypeptides with molecular weights of 50,000, 56,000, 60,000, 70,000, and 74,000 and with molar ratios of 1:2:2:1:1, respectively. Autoradiography showed P56 to be the only major virus-induced polypeptide; the other proteins are apparently of host cell origin. Electron microscopic examination suggested a cartwheel shape for the polymerase complex which was seen to dissociate as polyadenylic acid was added. Antibody previously shown to inhibit enzyme activity aggregated the 70S units.
Mechanism of coliphage M13 contraction: intermediate structures trapped at low temperatures
Authors: Manning M , Chrysogelos S , Griffith J
Published: January 2020

The filamentous coliphage M13 can be transformed into a spherical particle (termed spheroid) by exposure to an interface of water and slightly polar but hydrophobic solvent such as chloroform-water at 24 degrees C. We report here that exposure of M13 filaments to a chloroform-water interface at 2 degrees C trapped the phage particles in forms morphologically intermediate to filaments and spheroids. These structures were rods 250 nm long and 15 nm wide, and each had a closed, slightly pointed end, an open flaired end, and a hollow central channel. The final contraction of these intermediates (termed I-forms) into spheroids was dependent upon both temperature and the presence of the solvent-water interface but was apparently independent of both the minor phage coat proteins and the virion DNA. Although stable in an aqueous environment, I-forms, in contrast to filaments, were readily disrupted by detergents, suggesting that the phage structure had been altered to a form more easily solubilized by membrane lipids. These solvent-induced changes might be related to the initial steps of phage penetration in vivo.
Cleavage of the Capsid Protein Precursors of Encephalomyocarditis Virus in Rabbit Reticulocyte Lysates
Authors: Shih Chao-Yun T. , Shih Ding S.
Published: January 2020

The cleavage pathway of the three capsid protein precursors of encephalomyocarditis virus, proteins A1, A, and B, was studied in rabbit reticulocyte lysates. Kinetic data suggested that the three proteins were cleaved through a sequential of A1 to A to B.
Shope fibroma virus. II. Role of the virion-associated nucleases
Authors: Pogo B G , Stein A , Freimuth P
Published: January 2020

The effect of Shope fibroma virus (SFV) infection on host DNA synthesis was investigated. The cytocidal strain, SFV-I, inhibited the incorporation of [3H]thymidine into nuclear DNA very shortly (2 h) after infection, whereas the noncytocidal strain, SFV-W, did so later (10 h postinfection) and to a lesser extent. Furthermore, a two- to threefold stimulation of host DNA synthesis was recorded in SFV-W-infected cells 3 to 4 h after infection. Since virion-associated nucleases have been implicated in the shutoff of host synthesis, these and other enzymatic activities were measured in purified virion preparations. The SFV strains and vaccinia virus contained equivalent amounts of DNA-dependent RNA polymerase, ATPase, and protein kinase activities. However, in SFV-W the pH 4.5 exonuclease activity was lower than in SFV-I and vaccinia virus, and the level of pH 7.8 endonuclease was almost undetectable. To test whether the lack of endonucleolytic activity had some effect on the removal of the cross-links in the parental DNA that occurs after viral penetration, the fate of the virion SFV DNA was followed. The majority (80%) of the SFV-I and SFV-W DNA molecules extracted after viral adsorption sedimented in alkaline sucrose gradients as cross-linked. After 3 h of infection, 75% of the SFV-I DNA molecules lacked cross-links, whereas 78% of the SFV-W DNA still remained cross-linked. The same results were obtained when the presence of cross-links was tested in restriction fragments. Taken together, these results indicate that virion-associated nucleases are involved in the early shutoff of host DNA synthesis and in the elimination of cross-links from the parental viral DNA.