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Temperature-sensitive changes in surface modulating assemblies of fibroblasts transformed by mutants of Rous sarcoma
Abstract:
The hypothesis that surface modulating assemblies containing microfilaments and microtubules and altered after cellular transformation was tested on cells infected with temperature-sensitive mutants of avian sarcoma virus. Untransformed cells (mouse 3T3 and chick fibroblasts), cells transformed by simian virus 40 (SV 3T3), and chick fibroblasts infected with Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV-A-infected cells) were first compared for differences in microfilament and microtubule patterns after treatment with fluorescein-labeled antibodies to actin and tubulin. Transformed cells showed disappearance of ordered stress microfilaments and thickened or diffuse alterations of microtubular arrays. At restrictive temperatures (41 degrees), chick fibroblasts infected with a temperature-sensitive mutant (ts 68) of Rous sarcoma virus showed normal patterns of stress fialments and radial microtubular arrays originating in 1 or 2 centrioles. At permissive temperatures (37 degrees), these patterns were disordered and resembled those of SR-RSV-A-infected cells. After a shift from 41 degrees to 37 degrees, the changes in microtubules were observed in the majority of cells within 1 hr. These changes were reversible and did not result from the inability of tubulin to polymerize. In ts 68-infected cells at permissive temperatures, concanavalin A induced much less surface modulation (inhibition of receptor mobility) than at restrictive temperatures. These results suggest that cellular transformation alters both the structure and function of surface modulating assemblies and prompt the hypothesis that products of viral transforming genes may affect these assemblies with a consequent loss of growth control.
Insights
Cellular transformation disrupts microfilaments and microtubules, affecting cell surface modulation. Viral transforming genes likely impact these assemblies, leading to loss of growth control.
Area of Science:
- Cell Biology
- Virology
- Cytoskeleton Dynamics
Background:
- Surface modulating assemblies, including microfilaments and microtubules, are crucial for cellular structure and function.
- Cellular transformation by viruses is known to alter cell morphology and behavior.
Purpose of the Study:
- To investigate the hypothesis that surface modulating assemblies are altered following viral-induced cellular transformation.
- To examine the impact of viral transforming genes on cytoskeletal organization and cell surface properties.
Main Methods:
- Comparison of microfilament and microtubule patterns in untransformed, SV40-transformed, and Rous sarcoma virus (RSV)-infected cells using immunofluorescence.
- Utilized temperature-sensitive mutants of avian sarcoma virus to study dynamic changes in cytoskeletal organization.
- Assessed surface modulation using concanavalin A binding assays.
Main Results:
- Transformed cells exhibited disorganized microfilaments and altered microtubule arrays compared to untransformed cells.
- Temperature-sensitive RSV infection led to reversible cytoskeletal disorganization at permissive temperatures.
- Cellular transformation significantly reduced concanavalin A-induced surface modulation.
Conclusions:
- Viral-induced cellular transformation profoundly alters the structure and function of surface modulating assemblies.
- The products of viral transforming genes are implicated in disrupting cytoskeletal organization and cell surface regulation.
- These alterations likely contribute to the loss of normal cellular growth control observed in transformed cells.