Synthesis and Glycosylation of Polyprotein Precursors to the Internal Core Proteins of Friend Murine Leukemia Virus

Evans, Lawrence C.; Dresler, Steven L.; Kabat, David

doi:10.1128/jvi.24.3.865-874.1977

Cited by 94 publications

(47 citation statements)

References 25 publications

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“…These results indicated that late leukemic spleen cells expressed a decreased amount of FV p15 cell surface antigens. Because p15 and p12 antigens are both encoded by the same viral gene and are expressed on the cell surface on the same polyprotein molecule (17,18), these results agreed with those using goat anti-p 12 serum, indicating that expression of gag-encoded proteins was reduced on late leukemic cells. However, in contrast to previous results with goat anti-gp70 serum, late leukemic spleen cells also expressed decreased F-MuLV gp70 as detected by monoclonal antibody.…”

Section: Analysis Of Fv Cell Surface Antigens On Early and Late Leukesupporting

confidence: 75%

New cell surface gp70 related to Friend mink cell focus-inducing virus is expressed on Friend virus-induced erythroleukemic spleen cells after elimination of ecotropic Friend virus gp70 in Rfv-3r/s mice.

Britt¹,

Collins²,

Chesebro³

1981

The Journal of Experimental Medicine

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Spleen cells from Rfv-3r/s mice with Friend virus-induced erythroleukemia were analyzed for expression of virus-induced proteins with monoclonal antiviral antibodies and conventional antisera. Leukemic spleen cells, 30-60 d after virus inoculation, expressed decreased amounts of ecotropic Friend murine leukemia helper virus gag- and env-encoded cell surface and intracellular proteins compared with leukemic cells tested 8-10 d after virus inoculation. In contrast, the spleen focus-forming virus-induced protein, gp55, was present on both leukemia cell populations. This difference appeared to be mediated by the humoral antibody response in Rfv-3r/s mice, which could recognize only ecotropic gag and env proteins, and not gp55. A new gp70 molecule cross-reactive with a recombinant Friend mink cell focus-inducing virus was found in large quantities on late leukemic cells. This protein appeared to be derived from a recombinant virus produced during the course of Friend virus infection. The appearance of this new gp70 suggests that recombinant viruses other than spleen focus-forming virus may play a role in Friend virus-induced erythroleukemia.

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Section: Analysis Of Fv Cell Surface Antigens On Early and Late Leukesupporting

confidence: 75%

New cell surface gp70 related to Friend mink cell focus-inducing virus is expressed on Friend virus-induced erythroleukemic spleen cells after elimination of ecotropic Friend virus gp70 in Rfv-3r/s mice.

Britt¹,

Collins²,

Chesebro³

1981

The Journal of Experimental Medicine

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“…Glycosylated Gag was found originally at the surface of murine leukemia cells infected with Gross leukemia virus and has been shown to contain the Gross cell surface antigen (22,44). It is now apparent that this protein is a universal feature of MuLV-infected cells (12,16,40) as well as feline leukemia virus-infected cells (30).…”

mentioning

confidence: 99%

Characterization of glycosylated Gag expressed by a neurovirulent murine leukemia virus: identification of differences in processing in vitro and in vivo

Fujisawa

McAtee

Zirbel

et al. 1997

J Virol

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The neuroinvasiveness of a chimeric murine retrovirus, CasFr KP (KP), is dependent on the expression of glycosylated Gag (gp85 gag). This viral protein is the product of alternate translation initiation 88 codons upstream of and in frame with the initiation codon of pr65 gag , the precursor of the viral core proteins. Although expression of glycosylated Gag affects virus spread in the spleen, it appears not to affect virus spread in vitro in fibroblast cell lines (J. L. Portis et al., J. Virol. 68:3879-3887, 1994). The differential effects of this protein in vitro and in vivo have not been explained, and its function is unknown. We have here compared the in vitro processing of this molecule with that expressed in spleens of infected mice. In vitro, gp85 gag was cleaved near the middle of the molecule, releasing the C-terminal half (containing capsid and nucleocapsid domains of pr65 gag) as a secreted glycoprotein. The N-terminal half of the protein was associated with the plasma membrane as a ϳ55-kDa glycoprotein bearing the matrix domain of pr65 gag as well as the N-terminal 88 residue L domain. This processing scheme was also observed in vivo, although two differences were seen. There were differences in N-linked glycosylation of the secreted form of the protein expressed in the spleen. In addition, whereas the membrane-associated species assumed the orientation of a type II integral membrane protein (N cyto C exo) in fibroblasts in vitro, a subpopulation of spleen cells was detected in which the N terminus of the protein was exposed at the cell surface. These results suggest that the differential effects of glycosylated Gag expression in vivo and in vitro may be related to differences in posttranslational processing of the protein.

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“…Recently, complementary DNAs (cDNAs) that encode cell surface receptors for mouse ecotropic retroviruses (1, the medium overlying cell cultures for 2 h at 37°C. Cell monolayers were rinsed and then sequentially incubated for 1 h at 37°C with goat antiserum made to gp7O (12) and then with fluorescein-conjugated rabbit anti-goat antibody (Zymed Laboratories, Burlingame, Calif.) as described previously (20). After the cells had been rinsed three times with culture medium for 10 min per rinse, cultures were fixed with cold methanol and mounted for fluorescence microscopy.…”

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confidence: 99%

Plasma membrane receptors for ecotropic murine retroviruses require a limiting accessory factor

Wang

Paul

Burgeson

et al. 1991

J Virol

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A retroviral vector was used to express various amounts of the receptor (ecoR) for ecotropic host range murine retroviruses on naturally barren hamster, mink, and human cells. These cells and murine cells were then incubated for 2 h with dilutions of a helper-free ecotropic retrovirus that encodes human growth hormone, and the number of infected cells was later determined by growth hormone-specific immunofluorescence. For all cells under the conditions of these studies, virus adsorption was the limiting step of infection and the cellular capacities for infection were unsaturated either at cell surfaces or at intracellular sites. Thus, infections occurred at low multiplicities of infection per cell and were directly proportional to virus and cell concentrations, and only a small percentage (ca. 5%) of the infectious virions became adsorbed from the medium during the 2-h incubations. Although increasing the adsorption by raising virus or cell concentrations results in more infections in the cultures, increasing adsorption by raising the number of ecoR above a low threshold had no effect on infections. Thus, cells with a low number of ecoR were infected as efficiently as highly adsorbing cells that contained many times more ecoR. To reconcile these results, we conclude that only a small, set number of cell surface ecoR can be functional for infection and that all excess ecoR can only bind virus into an unsalvageable pool. Therefore, retroviral receptors on single cells are functionally diverse. Our results suggest that activity of ecoR in infection requires a limiting second cellular component. * Corresponding author. 25) and for gibbon ape leukemia virus (39) were isolated. Although these receptors appear to be unrelated, they both may be glycoproteins with multiple membrane-spanning regions (1, 39). The ecotropic receptor (ecoR) occurs on cells of mice and rats but not on cells of other species. Genetic analysis has suggested that ecoR may be essential for the viability of cultured murine fibroblasts (16). In this study, we have developed efficient methods to express ecoR cDNA in nonmurine cells. We used these cells to study the role of ecoR in virus binding and infection. Our results suggest that a cellular component in addition to ecoR is required for infection. MATERIALS AND METHODS Cells and viruses. Swiss mouse NIH 3T3 fibroblasts, mink lung CCL64 fibroblasts, Chinese hamster ovary cells (CHO), and human osteogenic sarcoma cells (Ostk-) were from American Type Culture Collection (Rockville, Md.). Ii-2 ecotropic packaging cells (34) and PA-12 amphotropic packaging cells (38) were from R. C. Mulligan (Massachusetts Institute of Technology, Cambridge) and A. D. Miller (Fred Hutchinson Cancer Center, Seattle, Wash.), respectively. CHO cells were grown in alpha minimum essential medium supplemented with 10% fetal bovine serum. Other cells were maintained in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum. Helper-free ecotropic host range viruses from ti-2 cells that encoded the neomycin...

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Synthesis and Glycosylation of Polyprotein Precursors to the Internal Core Proteins of Friend Murine Leukemia Virus

Abstract: Synthesis and post-translational processing of murine leukemia virus proteins were analyzed in a murine cell line (Eveline) that produces large amounts of Friend lymphatic leukemia virus. Immunoprecipitation of L-[35S]methionine-la

Cited by 94 publications

References 25 publications

New cell surface gp70 related to Friend mink cell focus-inducing virus is expressed on Friend virus-induced erythroleukemic spleen cells after elimination of ecotropic Friend virus gp70 in Rfv-3r/s mice.

New cell surface gp70 related to Friend mink cell focus-inducing virus is expressed on Friend virus-induced erythroleukemic spleen cells after elimination of ecotropic Friend virus gp70 in Rfv-3r/s mice.

Characterization of glycosylated Gag expressed by a neurovirulent murine leukemia virus: identification of differences in processing in vitro and in vivo

Plasma membrane receptors for ecotropic murine retroviruses require a limiting accessory factor

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