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Frequent generation of oncogenes by in vitro recombination of TRK protooncogene sequences
Abstract:
Transfection of NIH 3T3 cells with cDNA clones containing either the entire coding sequences or the tyrosine protein kinase domain of the human TRK protooncogene results in the frequent generation of transforming genes. Activation of most of these TRK oncogenes involves acquisition of DNA sequences. These sequences, unlike those present in the original human TRK oncogene, are not derived from tropomyosin genes. The products of these in vitro-generated TRK oncogenes retain the parental tyrosine protein kinase activity and contain an intact carboxyl terminus. However, they exhibit distinct biochemical properties. Whereas some of them are nonglycosylated cytoplasmic molecules, others were found to be transmembrane glycoproteins. These results suggest that TRK oncogenes may induce malignant transformation by allowing their tyrosine kinase to interact with various substrates depending on the nature of their activating sequences. If so, the TRK kinase may serve as a pleiotropic marker to identify various cellular proteins whose unscheduled phosphorylation on tyrosine residues contributes to neoplastic transformation.
Insights
Transfecting NIH 3T3 cells with TRK protooncogene cDNA generated novel TRK oncogenes. These oncogenes, retaining tyrosine kinase activity, exhibited varied biochemical properties, suggesting a role in malignant transformation.
Area of Science:
- Molecular Biology
- Oncogenesis
- Cellular Signaling
Background:
- The TRK protooncogene encodes a receptor tyrosine kinase implicated in cellular growth and differentiation.
- Oncogenic activation of TRK can lead to uncontrolled cell proliferation and malignant transformation.
- Understanding the mechanisms of TRK oncogene activation is crucial for cancer research.
Purpose of the Study:
- To investigate the generation and properties of TRK oncogenes through transfection.
- To characterize the biochemical differences in TRK oncogene products.
- To explore the potential role of TRK oncogenes in neoplastic transformation.
Main Methods:
- Transfection of NIH 3T3 cells with human TRK protooncogene cDNA clones.
- Analysis of acquired DNA sequences in generated TRK oncogenes.
- Biochemical characterization of TRK oncogene products, including glycosylation and cellular localization.
- Assessment of tyrosine protein kinase activity.
Main Results:
- Transfection frequently generated TRK oncogenes with acquired DNA sequences, distinct from tropomyosin.
- The resulting TRK oncogene products retained tyrosine kinase activity and an intact carboxyl terminus.
- Products exhibited diverse biochemical properties, appearing as nonglycosylated cytoplasmic molecules or transmembrane glycoproteins.
- These findings suggest TRK oncogenes can induce transformation via varied substrate interactions.
Conclusions:
- TRK oncogenes can be generated in vitro, leading to malignant transformation.
- The biochemical diversity of TRK oncogene products implies varied mechanisms of action.
- TRK kinase may function as a marker for identifying proteins involved in neoplastic transformation through aberrant tyrosine phosphorylation.