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Identification by a random linker insertion method of a region which suppresses the transforming activity of the raf
F Ishikawa1, R Sakai, M Ochiai
1Carcinogenesis Division, National Cancer Center Research Institute, Tokyo, Japan.
Abstract:
Activation mechanism of raf oncogene was studied by applying in vitro mutagenesis to its cDNA. Previous studies suggested the presence of an activation suppressing sequence in the amino-terminal half of c-raf product. Loss of the sequence by genetic rearrangement was presumed to convert c-raf to possess transforming activity. To identify such sequence, we prepared cDNA mutants by random linker insertion. Synthetic oligonucleotide linker was inserted into the plasmid containing cDNA at a single and random site. Coupling two different mutants, in-frame deletion mutants were constructed systematically. Analysis of these deletion mutants revealed a region, the loss of which made c-raf activated.
Insights
Researchers identified a specific region in the c-raf gene. Loss of this sequence activates the raf oncogene, a key factor in cancer development.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The raf oncogene plays a crucial role in cell signaling pathways.
- Previous research suggested a suppressive sequence in the amino-terminal region of c-raf.
- Genetic alterations leading to the loss of this sequence were hypothesized to cause oncogenic activation.
Purpose of the Study:
- To elucidate the activation mechanism of the raf oncogene.
- To identify the specific sequence responsible for suppressing c-raf activity.
- To understand how the loss of this sequence confers transforming activity.
Main Methods:
- In vitro mutagenesis was applied to c-raf cDNA.
- Random linker insertion mutagenesis was used to create cDNA mutants.
- Systematic construction and analysis of in-frame deletion mutants were performed.
Main Results:
- A specific region within the c-raf gene was identified.
- Deletion of this identified region resulted in the activation of c-raf.
- This activation confers transforming activity to the c-raf protein.
Conclusions:
- The identified region acts as a negative regulator of c-raf activity.
- Loss or disruption of this regulatory sequence is a key step in raf oncogene activation.
- Understanding this mechanism provides insights into cancer development and potential therapeutic targets.