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Functional analysis of a retroviral host-range mutant: altered long terminal repeat sequences allow expression in
Abstract:
A retroviral host-range neomycin-resistant myeloproliferative sarcoma virus mutant, which is expressed in the embryonal carcinoma cell lines F9 and PCC4aza1R, was molecularly cloned and analyzed. This mutant virus, PCMV, differs from myeloproliferative sarcoma virus by two major deletions, one of which spans exactly a 75-base-pair repeat of the long terminal repeat. Functional analysis of recombinant viruses shows that the host-range expansion of PCMV is a property of nucleotide changes within the U3 region of the long terminal repeat. Furthermore, expression assays of chimeric long terminal repeats show that the enhancer region of PCMV joined to the promoter region of Moloney murine leukemia virus is sufficient to direct the synthesis of chloramphenicol acetyltransferase in F9 and PCC4 cells.
Insights
Researchers identified a myeloproliferative sarcoma virus mutant (PCMV) that infects embryonal carcinoma cells. Host-range expansion is linked to specific changes in the virus's long terminal repeat U3 region.
Area of Science:
- Retroviral research
- Molecular biology
- Cancer cell line studies
Background:
- Myeloproliferative sarcoma virus (MPSV) is a retrovirus.
- Embryonal carcinoma (EC) cell lines like F9 and PCC4aza1R are valuable models for early development and cancer research.
- Understanding retroviral host-range is crucial for gene therapy and viral vector development.
Purpose of the Study:
- To molecularly clone and analyze a novel retroviral host-range mutant.
- To identify the genetic determinants responsible for the expanded host range of this mutant virus in EC cells.
- To investigate the role of the long terminal repeat (LTR) in viral tropism.
Main Methods:
- Molecular cloning of the retroviral mutant PCMV.
- Sequence analysis to identify genetic differences between PCMV and MPSV.
- Functional analysis using recombinant viruses and chimeric LTRs.
- Expression assays measuring chloramphenicol acetyltransferase (CAT) activity.
Main Results:
- The myeloproliferative sarcoma virus mutant (PCMV) was successfully cloned and characterized.
- PCMV exhibits an expanded host range, efficiently infecting F9 and PCC4aza1R embryonal carcinoma cells.
- Key genetic alterations in PCMV include two major deletions within the LTR, one affecting a 75-base-pair repeat.
- Nucleotide changes within the U3 region of the LTR are responsible for PCMV's host-range expansion.
- A chimeric LTR, combining the PCMV enhancer with the Moloney murine leukemia virus promoter, effectively drives gene expression in EC cells.
Conclusions:
- The U3 region of the retroviral LTR is a critical determinant of host-range tropism in embryonal carcinoma cells.
- Specific nucleotide modifications within the LTR can confer the ability to infect previously resistant cell types.
- This study provides insights into the mechanisms of retroviral adaptation and offers potential for developing targeted viral vectors.