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Isolation and preliminary characterization of temperature-sensitive mutants of the murine sarcoma leukaemia virus
Abstract:
Five temperature-sensitive mutants (ts I to 5) were isolated from a stock of the Moloney strain of murine sarcoma leukaemia virus complex which had been mutagenized by ultraviolet irradiation or N-methyl-N'-nitro-N-nitrosoguanidine. In mouse cells at the non-permissive temperature the mutants formed fewer foci of transformed cells than at the permissive temperature. The ts mutants were characterized by testing: (I) murine leukaemia virus (MuLV) clones from the ts complex, (2) the effect of additional wild type MuLV on focus formation, (3) focus formation in rat cells and (4) focus formation with pseudotypes rescued from non-producer cells. Two mutants (ts 1 and ts 3) were found to be ts MuLVs which did not possess heat labile virion proteins and were not ts in post-penetration helper functions necessary for the fixation of sarcoma virus transformation. The remaining three mutants (ts 2, ts 4 and ts 5) were ts murine sarcoma viruses which, however, showed no temperature-sensitive effect on the maintenance of transformed cell morphology nor on colony forming efficiency in soft agar.
Insights
Five temperature-sensitive mutants of Moloney murine sarcoma leukaemia virus were identified. Two mutants were temperature-sensitive murine leukaemia viruses, while three were temperature-sensitive murine sarcoma viruses affecting transformation but not cell morphology.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Murine sarcoma leukaemia virus complex is a valuable tool for studying viral oncogenesis.
- Temperature-sensitive (ts) mutants are crucial for dissecting viral replication and transformation pathways.
Purpose of the Study:
- To isolate and characterize temperature-sensitive mutants of the Moloney murine sarcoma leukaemia virus complex.
- To differentiate between temperature-sensitive defects in murine leukaemia virus (MuLV) helper functions and murine sarcoma virus (MSV) transformation functions.
Main Methods:
- Isolation of ts mutants using chemical mutagens and UV irradiation.
- Characterization of mutants by assessing focus formation in mouse and rat cells at permissive and non-permissive temperatures.
- Analysis of MuLV clones, effect of wild-type MuLV, and pseudotype rescue from non-producer cells.
Main Results:
- Five ts mutants (ts 1-5) were isolated, showing reduced focus formation at non-permissive temperatures.
- Mutants ts 1 and ts 3 were identified as ts MuLVs, lacking heat-labile virion proteins and ts post-penetration helper functions.
- Mutants ts 2, ts 4, and ts 5 were ts MSVs, but did not exhibit temperature sensitivity in maintaining transformed cell morphology or anchorage-independent growth.
Conclusions:
- The study successfully isolated and categorized ts mutants of the Moloney murine sarcoma leukaemia virus complex.
- Distinct temperature-sensitive defects were identified, differentiating between MuLV helper functions and MSV transformation capabilities.
- The findings provide insights into the genetic basis of viral transformation and the roles of specific viral components.