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3Y1 rat cells are defective in processing of the envelope precursor protein of AKR virus
Abstract:
Rat 3Y1 cells were infected by AKR virus through microinjection of molecularly cloned proviral DNA. Based on a strong immunofluorescence using anti-p30 as an antiserum a cell clone (RESA-2) was selected that had a high expression of viral antigens. Subsequent restriction analysis of its DNA revealed that the RESA-2 clone contained at least 30 apparently intact integrated proviruses per genome. There was an apparently normal synthesis and processing of gag and pol gene products. The viral envelope precursor polyprotein gPr82env, however, did not yield the major envelope glycoprotein gp70. The gag precursor polyprotein, Pr65gag, as well as the gPr82env from RESA-2 cells were identified as AKR viral proteins by gel electrophoresis of hydroxylamine cleavage fragments. The virions formed by RESA-2 cells lacked gp70 and were noninfectious. After fusion of RESA-2 cells and mouse cells an infectious N-tropic virus was produced. The results indicate that rat 3Y1 cells lack (a) factor(s) necessary for the correct processing of gPr82env. The high incidence of abortive infections of murine leukemia virus (MLV) in susceptible rat cells reported by others is therefore probably due to defective particles in the virus stock and/or to the lack of (a) cellular factor(s) necessary for reverse transcription and subsequent integration of the viral genome.
Insights
Rat cells infected with AKR virus showed high viral antigen expression but produced noninfectious virions lacking key glycoproteins. This suggests rat cells may lack factors essential for proper viral processing and infection.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Murine leukemia virus (MLV) infections in rat cells are often abortive.
- The underlying reasons for this low infectivity are not fully understood.
Purpose of the Study:
- To investigate the molecular mechanisms behind abortive MLV infections in rat cells.
- To identify cellular factors potentially involved in viral replication.
Main Methods:
- Infection of rat 3Y1 cells with AKR virus via proviral DNA microinjection.
- Selection and characterization of a high-antigen-expressing cell clone (RESA-2).
- Analysis of viral gene product synthesis, processing, and virion composition.
Main Results:
- RESA-2 cells contained numerous integrated proviruses but produced defective virions lacking gp70.
- Viral gag and pol gene products were synthesized and processed normally.
- Fusion with mouse cells rescued infectious virus production, indicating a defect in rat cells.
Conclusions:
- Rat 3Y1 cells appear to lack essential factors for correct processing of the viral envelope precursor (gPr82env).
- This cellular deficiency may explain the high rate of abortive MLV infections in rat cells.
- Defective viral particles or lack of cellular factors for reverse transcription/integration could also contribute.