Related Experiment Videos
Envelope gene sequence of two in vitro-generated mink cell focus-forming murine leukemia viruses which contain the
Abstract:
The mink cell focus-forming (MCF) class of recombinant murine leukemia viruses (CI-1 to 4) were isolated from iododeoxyuridine-induced C3H/MCA 5 cells in culture and molecularly cloned. These genomes included infectious (CI-3) and defective (CI-4) recombinants. A total of 2,408 nucleotides of CI-3 virus DNA, including the MCF envelope gene, were sequenced and compared with ecotropic, dual-tropic, and xenotropic sequences. The extent of recombinational exchange in CI-3 was from 145 nucleotides 3' of the splice acceptor site for the envelope mRNA to nucleotide 1,722, between the end of gp70 and the beginning of Prp15E. Thus, the entire gp70 sequence of the endogenous nonecotropic parent was present in this recombinant. The nature and location of the recombinant junctions were consistent with a mechanism involving DNA exchange during reverse transcription. Comparison of the substituted sequence in CI-3 with that of Moloney MCF virus suggests a very close relationship, if not identity, between the endogenous dual-tropic proviruses from which they were derived. A nonidentity of xenotropic and MCF gp70s was observed, suggesting that xenotropic murine leukemia viruses are not the nonecotropic parent of the env gene of MCF murine leukemia viruses. The replication-defective virus CI-4 had a 684-nucleotide deletion present in the env gene, eliminating the hydrophobic regions within the gp70 carboxy end and the p15E amino end. This sequence was bordered by an 11-nucleotide direct repeat in CI-3 viral DNA.
Insights
Researchers sequenced mink cell focus-forming (MCF) virus DNA, revealing recombinational exchange in the envelope gene. This suggests xenotropic murine leukemia viruses are not the parent of MCF virus env genes.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Mink cell focus-forming (MCF) viruses are recombinant murine leukemia viruses implicated in various biological activities.
- Understanding the genetic origins and structure of MCF viruses is crucial for deciphering their pathogenic potential.
- Previous studies have suggested complex origins for MCF viruses, involving recombination between different murine leukemia virus (MuLV) classes.
Purpose of the Study:
- To molecularly clone and sequence infectious and defective MCF virus isolates (CI-3 and CI-4).
- To compare the envelope (env) gene sequences of MCF viruses with other MuLV classes (ecotropic, dual-tropic, xenotropic).
- To elucidate the mechanism and extent of recombinational events in MCF virus genome formation.
Main Methods:
- Isolation and molecular cloning of recombinant murine leukemia viruses (CI-1 to CI-4) from cultured cells.
- DNA sequencing of 2,408 nucleotides of CI-3 virus, including the MCF env gene.
- Comparative sequence analysis of CI-3 env gene with ecotropic, dual-tropic, and xenotropic MuLV sequences.
Main Results:
- The infectious CI-3 virus exhibited extensive recombinational exchange within its env gene, spanning from nucleotide 145 to 1,722.
- The entire gp70 sequence of the endogenous nonecotropic parent was present in CI-3, suggesting a specific recombination event.
- Sequence comparison indicated a close relationship between CI-3 and Moloney MCF virus, but xenotropic and MCF gp70 sequences were non-identical, excluding xenotropic viruses as direct parents of the MCF env gene.
Conclusions:
- The recombination mechanism likely involves DNA exchange during reverse transcription.
- Xenotropic murine leukemia viruses are unlikely to be the direct nonecotropic parent of the MCF virus env gene.
- The defective CI-4 virus contained a significant deletion in the env gene, highlighting the variability within MCF virus isolates.