Activation of a human c-K-ras oncogene

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Human lung carcinomas PR310 and PR371 were identified to possess activated c-K-ras oncogenes.
• A mutation at codon 12 of the first coding exon in the PR371 oncogene substitutes cysteine for glycine in the p21 protein.
• The PR310 tumor's transforming gene features a mutation in the second coding exon.

Purpose of the Study:

• To investigate the transforming potential of specific mutations within the c-K-ras oncogene.
• To analyze the impact of mutations at codons 12, 61, or both on the oncogenic activity of p21 proteins.
• To explore the functional interchangeability of ras gene coding exons.

Main Methods:

• Construction and analysis of c-K-ras/c-H-ras chimeric genes.
• Point mutation analysis at specific codons (12 and 61) of the c-K-ras gene.
• Cell transformation assays using NIH3T3 cells to assess oncogenic potential.

Main Results:

• An A-T transversion at codon 61 in the PR310 c-K-ras gene results in histidine incorporation instead of glutamine in the p21 protein.
• The codon 61 mutation alone is sufficient to confer transforming potential to ras genes.
• Hybrid ras genes with mutations at both codons 12 and 61 also demonstrate transforming capability in NIH3T3 cells.
• Coding exons of ras genes are interchangeable, with chimeric p21 ras proteins retaining oncogenic ability.

Conclusions:

• Specific point mutations in the c-K-ras oncogene, particularly at codons 12 and 61, are critical for conferring transforming activity.
• The functional domains of ras proteins can be modulated by mutations at distinct sites, affecting oncogenesis.
• Exon shuffling within ras genes maintains oncogenic potential, highlighting the robustness of the ras transforming mechanism.