PubMed Health⌕ Search

Biomedical subjects

P Tegtmeyer

Publications and source records attributed to P Tegtmeyer.

71 records · Page 4Linked to original sources
PubMed1977

Identification of simian virus 40 protein A.

A large simian virus 40 (SV40)-specific protein can be efficiently immunoprecipitated from infected cell extracts with antisera obtained from hamsters bearing SV40-induced tumors. The protein has an apparent molecular weight of 88,000 to 100,000 with respect to markers with known molecular weights, but behaves anomalously on sodium dodecyl sulfate (SDS)-polyacrylamide gels. Cell lines infected by two different strains of SV40 synthesize immunoreactive proteins that differ slightly in mobility during SDS-polyacrylamide gel electrophoresis, evidence that the protein is coded for by the virus. These differences in protein size correlate with differences in the electrophoretic mobility of viral DNA fragments obtained by digestion with HindII and III restriction enzymes. The size of the viral capsid proteins VP2 and VP3 also varies with the strain of virus. dl-1001, a constructed deletion mutant that lacks part of the SV40A gene, directs the synthesis of a 33,000-dalton polypeptide that is not detected in cells infected with wild-type virus. The deletion fragment, like the larger protein, is phosphorylated. Maps of tryptic peptides from the 88,000- to 100,000-dalton protein and the 33,000-dalton fragment show common peptides and provide strong direct evidence that the proteins are products of the SV40 A gene. The deletion fragment reacts with antitumor sera and binds to double-stranded DNA in the presence of the complete A protein.

Capsid↗
PubMed1977

Modification of simian virus 40 protein A.

The A protein of simian virus 40 is phosphorylated in both productive and transforming infection. The phosphorylated amino acid has been identified as serine and has been localized in a single tryptic peptide of the protein. Because the A protein synthesized in infection by A mutants is phosphorylated to the same extent and in the same peptide as in infection by wild-type virus, the functional defect of the A mutants is apparently unrelated to phosphorylation. At least three distinct forms of the A protein with apparent molecular weights of 85,000, 88,000, and 100,000 can be identified in extracts of cells infected by wild-type virus. After exposure of cells to Nonidet P-40, the 85,000- and 88,000-dalton proteins were found in varying amounts in extracts of permissive cells but not in extracts of transformed cells. This finding raised the question of the possible functional importance of the smaller proteins in productive infection. However, the virtual absence of the 85,000- and 88,000-dalton proteins in some extracts of the fully permissive CV-1 cell line indicates that a conversion of the larger to the smaller forms of the A protein is not required in significant quantity for productive infection. Furthermore, a study of extraction conditions shows that the smaller proteins are easily generated during extraction and provides an explanation for the appearance of these proteins in some cells after extraction under unfavorable conditions.

Cell Line↗
PubMed1975

Function of simian virus 40 gene A in transforming infection.

In productive infection by simian virus 40, the A gene is known to regulate the initiation of viral DNA replication and to control the synthesis of late viral RNA. The function of the A gene in transforming infection was investigated by the infection of a variety of cell species with six independently isolated temperature-sensitive mutants belonging to the A complementation group. The A mutants failed to initiate the stable transformation of cells during continuous infection at the restrictive temperature. After the establishment of transformation at the permissive temperature and a subsequent shift to the restrictive temperature to block the A function, however, two distinct virus-cell interactions were identified. In one case, the increased colony-forming capacity of transformed cells remained stable after the temperature shift. In the other case, the temperature shift decreased the capacity of transformed cells to form colonies to the level of untransformed control cells. The outcome of the virus-cell interaction depended both on the nature of the A mutation in a given cell species and on the species of the cell transformed by a given mutant. These findings suggest that the transformation process may require two distinct events, each related to A gene expression.

Animals↗
PubMed1975

Regulation of tumor antigen synthesis by simain virus 40 gene A.

Simian virus 40 gene A has previously been shown to promote the replication of viral DNA and the transcription of late viral RNA in productive infection and to maintain the growth characteristics of some transformed cells. The present study examines the effect of the A function on proteins synthesized during productive and transforming infections. Under restrictive conditions, temperature-sensitive A mutants induce the overproduction of a 100,000-dalton protein both in productively infected monkey cells and in transformed rabbit cells. Immunoprecipitation of the induced protein with antisera, prepared against simian virus 40-induced tumors in hamsters, was used to identify the induced protein as tumor antigen. The same protein can be precipitated from extracts of cells infected by wild-type virus but not from uninfected cells. Furthermore, the mutant-induced protein is more rapidly degraded in vivo and is less tightly bound to intranuclear components than the protein induced by wild-type virus. The presence of the same virus-induced protein in infected cells from different species and the altered behavior of that protein in mutant infection strongly suggest that the protein is virus coded. Because the protein is large enough to account for the entire coding capacity in the early region of the simian virus 40 genome, the 100,000-dalton protein may well be the primary product of the only early gene identified by complementation studies, the A gene. If the 100,000-dalton protein that is overproduced in mutant infection is the A protein and the only early protein, then functional wild-type A protein must regulate its own synthesis in both productive and transforming infections.

Animals↗
PubMed1974

Antigenic phenotypes and complementation groups of temperature-sensitive mutants of simian virus 40.

The antigenic phenotypes of several temperature-sensitive mutants of simian virus 40 were determined by an immunofluorescence microtechnique that allowed a very high degree of internal control for the conditions of virus infection and antigenic staining. The tumor (T), U, capsid protein (C), and virion (V) antigens were investigated. Productive infection in monkey cells and abortive infection in mouse cells were simultaneously monitored for antigen production at both permissive and restrictive temperatures. Complementation analyses of the mutants demonstrated two complementing groups (A and B) and one noncomplementing group ((*)). One of the complementing groups could be subdivided into two subgroups having very different antigenic phenotypes. The following phenotypes were observed at the restrictive temperature in monkey cells. (i) The noncomplementing group produced none of the antigens. (ii) Group A induced T antigen in moderately but consistently reduced numbers of cells. Other antigens were markedly reduced or absent. (iii) Some of the group B mutants produced T antigen but little or no U and V antigens. The C antigen appeared in the nucleolus and cytoplasm of this subgroup. (iv) In the other group B mutants, antigen synthesis was not altered. Similar phenotypes were observed in mouse cells, except that U, C, and V antigens could not be detected during either the mutant or wild-type virus infections at any temperature.

Animals↗
PubMed1974

Altered protein metabolism in infection by the late tsB11 mutant of simian virus 40.

The DNA of the temperature-sensitive mutant tsB11 is replicated at the same rate as the DNA of wild-type virus in infection at the restrictive temperature. The progeny mutant DNA cannot be distinguished from wild-type DNA by gel electrophoresis and is assembled into a nucleoprotein complex with the same velocity sedimentation characteristics as the wild-type complex. Analysis of in vivo protein synthesis by sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoprecipitation techniques demonstrated that the capsid components VP1, VP2, and VP3 of the mutant and wild-type virus are synthesized at a similar rate, but VP1 fails to accumulate within cells infected by tsB11. Furthermore, VP1 is located predominantly in the cytoplasmic rather than in the nuclear fraction of extracts from cells infected by the mutant. Immunofluorescent studies localized virion antigen within the nucleolus as well as the cytoplasm. The altered intracellular distribution and stability of VP1 suggest that it may be the mutant protein of tsB11. The synthesis of a 72,000 dalton protein is consistently induced in significant quantity in cells infected by tsB11 at the restrictive temperature. A protein of the same apparent molecular weight is present in smaller quantities in uninfected cells and is only slightly increased in quantity in cells infected by wild-type virus.

Animals↗
PubMed1973

Relationship of replication and transcription of Simian Virus 40 DNA.

RNA produced by the Simian Virus 40 (SV40) mutant tsA30 during lytic infection of kidney cells of African green monkeys was examined by RNA-DNA competition-hybridization. This mutant is temperature-sensitive in a function (gene A) that regulates synthesis of viral DNA. No detectable difference between mutant RNA synthesized at the permissive temperature (33 degrees ) and wild-type viral RNA was found. During continuous infection with the mutant at the restrictive temperature (41 degrees ) only early viral RNA was produced. When mutant DNA and late RNA synthesis were initiated at the permissive temperature, a shift to the restrictive temperature rapidly terminated synthesis of viral DNA but not that of late viral RNA. The data indicate that the function of gene A is required before synthesis of late viral RNA and that after initiation, the production of late RNA continues without further expression of gene A or concomittant viral DNA synthesis.

Animals↗
PubMed1972

Simian virus 40 deoxyribonucleic acid synthesis: the viral replicon.

Three temperature-sensitive (ts) mutants of simian virus 40 (SV40) in complementation group A (tsA7, tsA28, tsA30) have been isolated and characterized in permissive and restrictive host cells. At 41 C in the AH line of African green monkey kidney cells, the mutants are deficient in an early function required to produce infectious viral deoxyribonucleic acid (DNA). Temperature-shift experiments and analysis of SV40 viral DNA replication by gel electrophoresis have provided strong evidence that the ts gene product of the three mutants is directly required to initiate each new round of viral DNA replication but is not required to complete a cycle which has already begun. The synthesis of mutant DNA molecules themselves can be initiated by a nonmutant gene product in viral complementation studies at 41 C. The cell, however, cannot substitute a host function to provide the initiator required for the replication of free viral DNA. The viral initiator is also required to establish the stable transformation of 3T3 cells.

Animals↗
PubMed1972

Simian virus 40 deoxyribonucleic acid synthesis: analysis by gel electrophoresis.

An agarose-gel electrophoresis technique has been developed to study simian virus 40 deoxyribonucleic acid (DNA) synthesis. Superhelical DNA I, relaxed DNA II, and replicative intermediate (RI) molecules were clearly resolved from one another for analytical purposes. Moreover, the RI molecules could be identified as early or late forms on the basis of their electrophoretic migration in relation to that of DNA II. The technique has been utilized to study the kinetics of simian virus 40 DNA synthesis in pulse and in pulse-chase experiments. The average time required to complete the replication of prelabeled RI molecules and to convert them into DNA I was approximately 10 min under the experimental conditions employed.

Animals↗
PubMed1972

Synthesis and assembly of simian virus 40. II. Synthesis of the major capsid protein and its incorporation into viral particles.

African green monkey kidney cells infected by simian virus 40 were analyzed for the presence of the major capsid protein (capsid protein I) by immunological and radiolabeling techniques. Antisera with different specificities were prepared by immunization with intact or denatured viral particles. Antisera prepared against intact virus reacted by complement fixation with viral particles and with an 8S subunit containing the capsid protein I. Antisera prepared against denatured viral particles reacted with unassembled capsid protein(s) as well as with viral particles. These antisera were used to detect 8S viral subunits or unassembled viral capsid protein in soluble extracts of infected cells after centrifugation at 100,000 x g to remove viral particles. The soluble antigen pool was found to be small during infection with wild-type virus or a temperature-sensitive mutant deficient in the synthesis of viral particles. Pulse-chase experiments, performed at a high multiplicity of infection, also indicated a small pool of nonparticle capsid protein I. Radioactive lysine was incorporated into capsid protein I of virus particles during a 2-hr pulse. A subsequent chase with excess unlabeled lysine resulted in only a slight increase in the radio-activity found in capsid protein I of viral particles. Furthermore, in the same experiments, capsid protein I was incorporated preferentially into empty shells during the pulse with a shift in radioactivity to intact virions during the chase period, indicating a possible precursor relationship between the two types of virus particles.

Animals↗
PubMed1972

Proposal for a uniform nomenclature for simian virus 40 mutants.

A uniform nomenclature for simian virus 40 mutants has been developed. This nomenclature should evolve into a comprehensive nomenclature as new mutants and information are obtained. Hopefully, his nomenclature will also stimulate the development of a comprehensive nomenclature for all animal virus mutants.

Genetic Complementation Test↗
PubMed1971

Temperature-sensitive mutants of simian virus 40: infection of permissive cells.

Ten temperature-sensitive mutants of simian virus 40 have been isolated and characterized in permissive cells. The mutants could be divided into three functional groups and two complementation groups. Seven mutants produced T antigen, infectious viral deoxyribonucleic acid (DNA), and structural viral antigen but predominantly the empty shell type of viral particles. Two mutants produced T antigen and infectious viral DNA, but, although viral structural protein(s) could be detected immunologically, no V antigen or viral particles were found. These two functional groups of mutants did not complement each other. A single mutant was defective in the synthesis of viral DNA, viral structural antigens, and viral particles. T antigen could be detected in infected cells by fluorescent antibody but was reduced by complement fixation assay. This mutant stimulated cell DNA synthesis at the restrictive temperature and complemented the other two functional groups of mutants.

Animals↗
PubMed1970

Inactivating and mutagenic effects of nitrosoguanidine on simian virus 40.

N-methyl-N'-nitro-N-nitrosoguanidine (NTG) in high concentrations inactivates extracellular simian virus 40. No mutants were found in stocks of virions partially inactivated by NTG under the experimental conditions employed. In contrast, NTG in low concentrations inhibits the intracellular replication of simian virus 40 and is an effective mutagen of the intracellular virus. Six temperature-sensitive mutants of simian virus 40 have been isolated for genetic studies of the virus and its interaction with mammalian cells.

Animals↗
PubMed1970

Morphological changes in productive and abortive infection by feline herpesvirus.

Feline herpesvirus produces characteristic morphological alterations in feline kidney cells. Nucleocapsid particles are formed in infected nuclei and are enveloped as they pass through the modified inner nuclear membrane. Aggregates of dense granular material and filamentous structures also regularly appear in infected nuclei. Infection of human embryonic lung cells by feline herpesvirus results in the appearance of intranuclear inclusion bodies, aggregates of dense granular material, and bundles of parallel filaments but no nucleocapsid particles.

Animals↗