PubMed Health⌕ Search

Biomedical subjects

E Fleissner

Publications and source records attributed to E Fleissner.

At least 19 recordsLinked to original sources
PubMed1979

Structural studies of retroviruses: characterization of oligomeric complexes of murine and feline leukemia virus envelope and core components formed upon cross-linking.

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

AKR murine leukemia virus↗
PubMed1979

Polymorphism of B-tropic leukemia viruses from BALB/c mice: association of a p30 antigen with N- versus B-tropism.

Comparison of a number of murine leukemia virus clones by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed extensive protein polymorphism among B-tropic, but not N-tropic, isolates from BALB/c mice, particularly in migration of p30 proteins. A type-specific radioimmunoassay for p30 was developed which uniformly discriminated all B-tropic viruses from N-tropic viruses of BALB/c origin. N- and B-tropic viruses of C57BL/6 and AKR Fv-1b/b origin could also be distinguished by this assay.

Animals↗
PubMed1978

Relationships of gp70 of MuLV envelopes to gp70 components of mouse lymphocyte plasma membranes.

The family of glycoproteins called gp70 includes molecules that are the main constituent of murine C-type viral envelopes, and some that are expressed as mendelian constituents of thymocyte plasma membranes in the absence of virions. To investigate further the relation of viral gp70s to plasma- membrane gp70s we compared peptide maps of gp70s derived by immunoprecipitation from cells infected with chosen viruses and from various thymocytes and leukemiacells known to express one or more of three immunogenetically defined gp70 types: Glx-gp70, X-gp70, and O-gp70. Maps of gp70 from cultured cells infected with ecotropic and xenotropic viruses were distinguishable from one another, and in general resembled gp70 maps prepared directly from ecotropic and xenotropic virions respectively. Maps of gp70s immunoprecipitated from thymocytes of five mouse strains and from two A strain T-cell leukemias also fell into two distinguishable and generally corresponding patterns. Thus peptide-mapping substantiates earlier conclusions that viral gp70s and plasma-membrane gp70s inherited independently of virus-production are highly related or identical molecules. The gp70 maps of thymocytes from B6, B6-G(+IX), 129, and A mice formed a group resembling the map from cultured cells infected with xenotropic virus. Thymocytes from AKR mice, and the two A strain leukemias, gave gp70 maps conforming more to the second pattern, that of cultured cells infected with ecotropic virus. This second pattern probably comprises at least two gp70 types, one of which is X-gp70. Our data indicate that the G(IX)-gp70 and O-gp70 sub-species of gp70 expressed in the cell populations we have studied are coded by xenotropic viral genomes, and X-gp70 by ecotropic viral genomes.

Animals↗
PubMed1977

Characterization of molecular species carrying gross cell surface antigen.

The Gross cell surface antigen (GCSA), associated with expression of endogenous Gross-type murine leukemia virus (G-MuLV) in tissues of mice, is defined by the cytotoxic reaction of a C57BL/6 antiserum, anti-AKR spontaneous leukemia K36, with cells of the Gross virus-induced C57BL/6 leukemia, Emale symbolG2. Sequential lactoperoxidase-catalyzed radioiodination of Emale symbolG2 cells, Nonidet P-40 lysis, precipitation with anti-K36 serum, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis identified molecules with properties of polyproteins encoded by the gag region of the viral genome. These cell surface species could also be labeled by in vitro culturing of Emale symbolG2 with radioactive glucosamine. The viral specificity of these molecules and their participation in the GCSA typing system were established as follows. (i) Absorption of anti-K36 serum with GCSA(+), but not GCSA(-), leukemias led to a marked decrease in precipitation of these proteins. (ii) The same Emale symbolG2 cell surface proteins were also precipitated by antisera against the MuLV virion proteins p30 and p15. (iii) Anti-K36 was shown to possess antibodies against Gross virus p30 and p15. (iv) "Clearing" the Emale symbolG2 lysate of molecules reactive with anti-p30 or anti-p15 sera removed molecules reactive with anti-K36 serum. (v) Absorption of anti-K36 serum with disrupted G-MuLV virions or with Gross p30 or p15 removed GCSA cytotoxic antibodies; partial absorption was achieved with disrupted Rauscher-MuLV (R-MuLV) or with R-MuLV p30, and no absorption was found with R-MuLV p15. These data show that Emale symbolG2 cells express, on their surfaces, MuLV core polyproteins that apparently can be glycosylated and on which the determinants of GCSA are located.

AKR murine leukemia virus↗
PubMed1977

Two species of type C viral core polyprotein on AKR mouse leukemia cells.

Two species of glycosylated type C viral core polyprotein were identified on the surface of AKR spontaneous leukemia cells. One of these cell surface polyproteins was shown by immunoprecipitation to have antigenic determinants of murine leukemia virus p30, p15, p12, and p10; the other had murine leukemia virus p30, p15, and p12, but not p10, determinants. Both species were also expressed on thymocytes from 6-month-old, preleukemic AKR mice.

Animals↗
PubMed1976

Leukemogenic activity of murine type C viruses after long-term passage in vitro.

Cloned stocks of several murine leukemia viruses (MuLVs) were shown to be leukemogenic for susceptible mice after more than nine years of in vitro passaging in mouse embryo fibroblasts. Tissue culture-grown Rauscher (R-) MuLVs injected into newborn or young adult BALB/c mice induced lymphocytic leukemias in 100% of the animals beginning 80 days post-inoculation. No erythroblastic leukemia was observed even after passaging the tissue-culture-grown R-MuLVs twice through mice, indicating that the component responsible for that disease had been lost or attenuated during growth in fibroblasts. The tissue-culture-grown stock of Moloney (M-) MuLVs likewise induced lymphocytic leukemias in 94% of injected newborn BALB/c mice, and the tissue culture-grown Gross (G-) MuLVs induced lymphocytic leukemias in 42% of injected newborn C3Hf mice. The host range and neutralization characteristics of viruses recovered from animals that became leukemic after injection with the tissue-culture-maintained MuLVs were found to be identical with those of the injected viruses. These data implicate the injected MuLVs in the induction of the leukemias and suggest that the capacity to induce the disease is stably inherited as part of the viral genome even in the absence of expression.

Animals↗
PubMed1976

X-gp70: a third molecular species of the envelope protein gp70 of murine leukemia virus, expressed on mouse lymphoid cells.

Three variants of the gp70 envelope component of MuLV are now recognizable serologically: GIX-gp70, 0-gp70, and X-gp70. The last of these, X-gp70, has so far been found only in mice or cells producing abundant C-type virus. This distinguishes X-gp70, provisionally, from the GIX-gp70 and 0-gp70 variants, each of which can be expressed on normal thymocytes without accompanying virus production, as exemplified by mouse strains 129 and B6, respectively. The X-gp70 genotype, however, is not limited to strains of mice-producing abundant virus, because X-gp70+ leukemias occur in strains of mice which do not produce a great deal of virus and whose thymocytes and other tissues are X-gp70-; this is analogous to the appearance of GIX+ leukemias in GIX- mouse strains.

Animals↗
PubMed1976

A core polyprotein of murine leukemia virus on the surface of mouse leukemia cells.

A polypeptide of molecular weight approximately 75,000 daltons, p(75), was identified on the surface of AKR spontaneous leukemia cells by lactoperoxidase-catalyzed radio-iodination. This protein was shown by immunoprecipitation to have antigenic determinants of MuLV p30, p15, and p10, but not gp70, suggesting that p(75) represents a polyprotein composed of virion core components. As evidenced by studies on incorporation of radioactive glucosamine, p(75) is probably glycosylated. No p(75) was found on 2 month old AKR thymocytes, and only a small amount of p(75) was detectable of thymocytes from 4 month old animals. However, substantial quantities of p(75) could be found on thymocytes from 6 month old, yet still preleukemic mice.

Age Factors↗
PubMed1976

High-titer replication of nondefective Sendai virus in MDBK cells.

Egg-grown Sendai virus was adapted to growth in a bovine kidney cell line (MDBK cells) by serial passage under defined conditions. The adapted virus contained only 50S RNA and was highly infectious for MDBK cells. Infection of these cells with a high multiplicity of adapted virus resulted in a yield of 10(8) MDBK-infectious units/ml by 18 h, accompanied by severe cytopathic changes in the host. Cell fusion did not occur. Examination of the proteins of the adapted virus revealed that despite the high infectivity of this virus for MDBK cells the virions contained considerable quantities of Fo, the precursor to the F glycoprotein that is responsible for cell fusion and high infectivity in other systems.

Adaptation, Biological↗
PubMed1976

Kinetics of utilization of Sendai virus RNA and protein in the process of virion assembly.

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.

Animals↗
PubMed1976

Presence of murine leukemia virus envelope proteins gp70 and p15(E) in a common polyprotein of infected cells.

The murine leukemia virus envelope proteins, p15(E) and gp70, exhibit a mode of processing distinct from that of virion core proteins according to three criteria. First, the incorporation of both p15(E) and gp70 into virions is more sensitive to the metabolic analogue 2-deoxy-D-glucose than the incorporation of core proteins. Second, the kinetics with which the newly synthesized envelope proteins appear in the released virions is delayed relative to the appearance of core proteins. Third, immunoprecipitation of large polypeptides from infected cells reveals the presence of gp70 and p15(E) in a common precursor distinct from the core polyprotein.

Cell Line↗
PubMed1975

Expression of murine leukemia virus envelope glycoprotein gp69/71 on mouse thymocytes. Evidence for two structural variants distinguished by presence vs. absence of GIX antigen.

Thymocytes of several mouse strains were tested for expression of the gp69/71 envelope component of murine leukemia virus by surface iodination, followed by immunoprecipitation and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Theses strains included two congenic lines differing from their partner stocks with respect to expression of GIX antigen demonstrable in the cytoxicity assay. We conclude that:(a) two structural variants of gp69/71 can be expressed on mouse thymocytes, (b) these are distinguishable by a small difference in mobility in SDS gels, (c) one carries GIX antigen and the other not, (d) they are coded, or their expression is regulated, by different chromosomal loci that are not closely linked, and (e) both can be expressed together on the thymocytes of inbred mice. In the intact thymocyte plasma membrane, the sites of group-specific antigen shared by the two gp69/71 variants, unlike the GIX type specificity carried by only one of them, are probably inaccessible to antibody.

Alleles↗
PubMed1975

Biochemical evidence linking the GIX thymocyte surface antigen to the gp69/71 envelope glycoprotein of murine leukemia virus.

It is known that the thymocyte surface antigen GIX is found in some strains of mice and not others, and that its expression in mice of strain 129, in which most extensive genetic studies have been made, is controlled by two unlinked cellular chromosomal loci. We have now isolated a protein with a mol wt of approximately 70,000 daltons from the surface of thymocytes from 129 mice, which have antigenic and biochemical properties characteristic of the gp69/71 envelope component of murine leukemia virus. Our evidence is compatible with the conclusion that it carries the GIX antigen.

Animals↗