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Suppression of tropomyosin synthesis, a common biochemical feature of oncogenesis by structurally diverse retroviral
Abstract:
To identify proteins whose production may be altered as a common event in the expression of structurally diverse oncogenes, we compared two-dimensional electropherograms of newly synthesized proteins from NIH/3T3 cell lines transformed by a variety of retroviral oncogenes, from cellular revertant lines, and from a line (433.3) which expresses the v-ras oncogene in response to corticosteroids. Most alterations in the synthesis of specific proteins detected by this approach appeared to be the result of selection during prolonged cultivation and were probably unrelated to the transformation process. However, we detected seven proteins whose synthesis was strongly suppressed in cell lines transformed by each of the six retroviral oncogenes we studied and whose production was fully or partially restored in two cellular revertant lines. Suppression of two of these proteins was also correlated with the initial appearance of morphological alteration during corticosteroid-induced oncogene expression in 433.3 cells. These proteins (p37/4.78 and p41/4.75) were identified as tropomyosins, a group of at least five cytoskeletal proteins. Transformation by the papovaviruses simian virus 40 and polyomavirus caused no suppression of synthesis of these tropomyosins. This indicates that suppression of tropomyosin synthesis is not a nonspecific response by cells to being forced to grow with the transformed phenotype but is specifically associated with oncogenesis by diverse retroviral oncogenes. The results are consistent with the hypothesis that the different biochemical processes initiated by expression of structurally diverse retroviral oncogenes may converge on a limited number of common targets, one of which is the mechanism which regulates the synthesis of tropomyosins.
Insights
Researchers identified seven proteins suppressed during retroviral oncogene transformation. These proteins, identified as tropomyosins, were restored in revertant lines, suggesting a common target in oncogenesis.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Oncogene expression drives cellular transformation.
- Identifying common molecular events in diverse oncogenesis is crucial.
Purpose of the Study:
- To identify proteins commonly affected by structurally diverse retroviral oncogenes.
- To investigate if tropomyosin synthesis is a shared target in retroviral oncogenesis.
Main Methods:
- Two-dimensional electropherograms of newly synthesized proteins were compared.
- NIH/3T3 cell lines transformed by various retroviral oncogenes were analyzed.
- Protein synthesis alterations were assessed in transformed, revertant, and induced oncogene expression cell lines.
Main Results:
- Seven proteins showed suppressed synthesis across six retroviral oncogene-transformed cell lines.
- Tropomyosin synthesis suppression was restored in cellular revertant lines.
- Suppression of tropomyosin synthesis was specific to retroviral oncogenes, not other transforming viruses like SV40 or polyomavirus.
Conclusions:
- Retroviral oncogene expression specifically suppresses tropomyosin synthesis.
- This suppression is a common event, suggesting a convergence on tropomyosin regulation.
- Tropomyosin synthesis regulation is a potential common target in oncogenesis induced by diverse retroviral oncogenes.