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Intracellular localization and processing of pp60v-src proteins expressed by two distinct temperature-sensitive
Abstract:
The transforming protein of Rous sarcoma virus, pp60v-src, is known to be a tyrosine protein kinase, but the mechanism of cell transformation remains unclear. In further investigating pp60v-src structure and function, we have analyzed two temperature-sensitive (ts) Rous sarcoma virus src gene mutants, tsLA29 and tsLA32. The mutations in tsLA29 and tsLA32 map in the carboxy-terminal region and the amino-terminal half of pp60v-src, respectively, and encode mutant proteins with either temperature-labile (tsLA29) or -stable (tsLA32) kinase activities. Here we examined the intracellular processing and localization of these pp60v-src mutants and extended our characterization of transformation parameters expressed by cells infected by the Rous sarcoma virus variants. No obvious defects in functional integrity of the tsLA32 pp60v-src could yet be demonstrated, whereas the tsLA29 pp60v-src was perturbed not only in kinase activity, but also in aspects of protein processing and localization. Analysis of transformation parameters expressed by infected cells demonstrated the complete temperature lability of both mutants.
Insights
Investigating Rous sarcoma virus mutants revealed that while both altered pp60v-src proteins caused temperature-sensitive cell transformation, one mutant also showed defects in protein processing and localization, impacting its kinase activity.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- The transforming protein pp60v-src is a tyrosine protein kinase central to Rous sarcoma virus-induced cell transformation.
- The precise mechanisms by which pp60v-src drives cell transformation are not fully understood.
Purpose of the Study:
- To investigate the structure-function relationship of pp60v-src using temperature-sensitive mutants.
- To analyze the intracellular processing, localization, and transformation capabilities of specific pp60v-src mutants.
Main Methods:
- Analysis of two temperature-sensitive Rous sarcoma virus src gene mutants (tsLA29 and tsLA32).
- Examination of intracellular processing and localization of mutant pp60v-src proteins.
- Characterization of transformation parameters in infected cells at varying temperatures.
Main Results:
- Mutations in tsLA29 and tsLA32 map to different regions of pp60v-src, affecting kinase activity stability.
- tsLA29 pp60v-src exhibited temperature-labile kinase activity, altered protein processing, and defective localization.
- tsLA32 pp60v-src showed temperature-stable kinase activity with no apparent functional defects.
- Both mutants induced complete temperature-sensitive cell transformation, indicating a link between pp60v-src function and transformation.
Conclusions:
- The study highlights the complex role of pp60v-src in cell transformation, involving kinase activity, protein processing, and localization.
- Defects in pp60v-src processing and localization, as seen in tsLA29, can contribute to transformation phenotypes.
- Further research into pp60v-src function is crucial for understanding viral oncogenesis.