Related Experiment Videos
Analysis of a deleted MC29 provirus: gag sequences are not required for fibroblast transformation
Abstract:
Recovered avian myelocytomatosis virus HBI is an MC29-related virus that induces lymphoid tumors in chickens rather than the predominant neoplastic disease induced by wild-type MC29 (namely, endotheliomas). An analysis of the structure of the HBI provirus(es) in the tumors demonstrated that the provirus(es) could be either full size or deleted. One tumor was found to be clonal in that it contained a single provirus which had been partially deleted; this raised a question concerning the role of this provirus in the maintenance of tumor growth. To characterize the detailed structure of this provirus and determine its biological activity, it was molecularly cloned from tumor DNA. Sequencing confirmed that the provirus contained a deletion which effectively removed the whole gag gene. However, the provirus was shown to encode a myc-specific protein, presumably initiating from within the myc gene, and to be biologically active when it was transfected onto quail embryo fibroblasts. Our results suggest that myc alone is sufficient to transform quail embryo fibroblasts and to maintain tumor growth in vivo.
Insights
Avian myelocytomatosis virus HBI causes lymphoid tumors in chickens. A deleted provirus lacking the gag gene still encodes a functional myc protein, sufficient for tumor growth.
Area of Science:
- Virology
- Oncology
- Molecular Biology
Background:
- Avian myelocytomatosis virus (MC29) typically causes endotheliomas.
- Recovered avian myelocytomatosis virus HBI induces lymphoid tumors in chickens.
- Tumor analysis revealed MC29-related HBI proviruses can be full-sized or deleted.
Purpose of the Study:
- To characterize the structure and biological activity of a deleted HBI provirus found in a clonal chicken tumor.
- To investigate the role of this specific provirus in maintaining tumor growth.
Main Methods:
- Molecular cloning of proviral DNA from tumor tissue.
- DNA sequencing to determine proviral structure.
- Transfection assays using quail embryo fibroblasts.
Main Results:
- Sequencing confirmed a deletion removing the entire gag gene in the cloned provirus.
- The deleted provirus encodes a functional myc-specific protein.
- Transfection demonstrated the virus's biological activity in quail embryo fibroblasts.
Conclusions:
- The myc oncogene alone is sufficient for transforming quail embryo fibroblasts.
- The deleted HBI provirus, expressing myc, can maintain tumor growth in vivo.