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Biochemical evidence that MCF murine leukemia viruses are envelope (env) gene recombinants
Abstract:
Recently, a novel class of murine type C virus (MCF), some strains of which are highly oncogenic in the AKR acceleration test, has been isolated from premalignant and malignant thymuses of AKR mice. The biology of these viruses suggested that MCFs are the product of recombination between endogenous ecotropic and xenotropic viruses and, further, that the recombination has taken place within the envelope (env) gene which encodes the surface glycoprotein (gp70) of the virion. We have compared by tryptic peptide analysis, the gp70s of four MCF isolates with the gp70s of various possible parental viruses. In addition, we have compared the tryptic peptides of the gag gene products p30 and p15 from several of these viruses. The results allow the following conclusions: (i) the gp70s of the MCF viruses are not identical to one another and are different from the gp70s of the possible parental viruses tested; (ii) the MCF virus gp70s have tryptic peptides in common with xenotropic virus gp70s as well as with ecotropic virus gp70s; and (iii) the gap region protein, p30, of the MCFs tested is identical to p30 of AKR ecotropic virus (Akv-1 or Akv-2) and distinct from p30 of xenotropic viruses, suggesting that the 5' end of the recombinant viruses is of Akv origin. The findings are discussed with respect to the possible role a recombinant virus might play in leukemogenesis in AKR mice.
Insights
Murine type C viruses (MCFs) isolated from AKR mice are recombinants of ecotropic and xenotropic viruses. Analysis of viral envelope (env) and gag genes suggests MCFs originate from AKR ecotropic viruses, potentially playing a role in leukemogenesis.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Murine type C viruses (MCFs) are implicated in leukemogenesis in AKR mice.
- MCFs are hypothesized to arise from recombination between endogenous ecotropic and xenotropic murine leukemia viruses.
- Recombination is suspected to occur within the viral envelope (env) gene, encoding the gp70 surface glycoprotein.
Purpose of the Study:
- To investigate the genetic origins of MCFs by comparing their envelope (gp70) and gag gene products with potential parental viruses.
- To determine if MCFs are indeed recombinants and to identify the source of their genetic material.
Main Methods:
- Tryptic peptide analysis was used to compare the gp70 proteins of four MCF isolates with those of potential parental viruses.
- Tryptic peptide analysis was also employed to compare the gag gene products (p30 and p15) of MCFs and parental viruses.
Main Results:
- The gp70 proteins of MCF viruses were distinct from each other and from parental viruses.
- MCF gp70 proteins shared tryptic peptides with both xenotropic and ecotropic virus gp70s.
- The gag p30 protein of MCFs was identical to that of AKR ecotropic viruses (Akv-1/Akv-2) and distinct from xenotropic viruses.
Conclusions:
- MCFs are recombinant viruses with genetic material derived from both ecotropic and xenotropic murine leukemia viruses.
- The gag gene of MCFs appears to originate from AKR ecotropic viruses, suggesting the 5' end of the recombinant genome is of AKR ecotropic origin.
- These findings support the role of recombinant MCFs in the development of leukemia in AKR mice.