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Friend erythroleukaemia cell mutants defective in viral gene expression
Abstract:
Cellular mutants defective in the expression of viral polypeptides were isolated from the Friend erythroleukemia cell line 745a by immunoselection with anti-ecotropic murine leukaemia virus serum in the presence of complement. The mode of appearance of the antiserum-resistant cells showed an interesting pattern which is discussed in the text. One of the mutants obtained contained no detectable gp70 or p15(E) while retaining gPr90env; defects appeared to reside in the processing of the gPr90env to gp70 and p15(E). In another type of mutant, gPr90env was not detected. All these mutants retained spleen focus-forming virus (SFFV)-specific gp55 and gag precursor Pr68gag. The mutants superinfected with the helper virus produced the helper and SFFV also, indicating that these mutations did not affect the replication of the exogenously infecting virus.
Insights
Researchers isolated cellular mutants resistant to Friend murine leukemia virus. Some mutants showed defects in viral glycoprotein processing, impacting gp70 and p15(E) expression, while retaining other viral proteins.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Friend erythroleukemia cells are a model for studying retroviral gene expression.
- Murine leukemia viruses encode envelope glycoproteins essential for viral entry and assembly.
- Understanding viral polypeptide processing is crucial for identifying mechanisms of viral replication.
Purpose of the Study:
- To isolate and characterize cellular mutants of Friend erythroleukemia cell line 745a defective in murine leukemia virus polypeptide expression.
- To investigate the specific defects in viral protein processing and their impact on viral gene expression.
Main Methods:
- Immunoselection using anti-ecotropic murine leukemia virus serum and complement to isolate resistant cells.
- Analysis of viral polypeptide expression in isolated mutants, focusing on envelope glycoproteins (gp70, p15(E), gPr90env) and gag proteins (Pr68gag, gp55).
Main Results:
- Isolation of cellular mutants exhibiting resistance to antiserum-mediated cell killing.
- Identification of mutants with defects in the processing of the precursor envelope glycoprotein (gPr90env) into mature gp70 and p15(E).
- Characterization of mutants lacking detectable gPr90env, indicating a block earlier in the processing pathway.
- Confirmation that spleen focus-forming virus (SFFV)-specific gp55 and gag precursor Pr68gag were retained in all mutants.
- Demonstration that these mutations did not impair the replication of superinfecting helper virus or SFFV.
Conclusions:
- Cellular mutations can specifically affect the post-translational processing of murine leukemia virus envelope glycoproteins.
- Defects in gPr90env processing lead to altered expression of gp70 and p15(E), impacting viral protein maturation.
- The identified mutations do not affect the replication machinery for exogenous viral infection, suggesting specific roles for the affected proteins in endogenous viral expression or assembly.