The Second Intron of the K-ras Gene Contains Regulatory Elements Associated with Mouse Lung Tumor Susceptibility

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-02, Vol.91 (4), p.1589-1593
• Main Authors: Chen, Bin, Johanson, Lisa, Wiest, Jonathan S., Anderson, Marshall W., You, Ming
• Format: Article
• Language: English
• Subjects: Adenoma; Adenoma - etiology; Adenoma - genetics; Alleles; Animals; Biochemistry; Biological and medical sciences; Cell lines; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; DNA, Neoplasm - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Neoplastic; Genes, ras - genetics; Genetic Predisposition to Disease; Genetic Variation; Genotype; Hybridity; Inbred strains; Introns; Introns - genetics; Lung Neoplasms - etiology; Lung Neoplasms - genetics; Lungs; Mice; Mice, Inbred Strains; Molecular and cellular biology; Nuclear Proteins - metabolism; Protein Binding; ras genes; Regulatory Sequences, Nucleic Acid - genetics; Repetitive Sequences, Nucleic Acid; Rodents; Sequence Analysis, DNA; Species Specificity; Tumor cell line; Tumors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.4.1589

We have previously demonstrated the preferential activation of the K-ras gene from the susceptible A/J parent in lung tumors from F1mouse hybrids. In the present study, the mechanism of this observation is further investigated. Higher levels of expression of A/J K-ras allele were detected in lung adenomas (30 of 30) from the C3A mouse. In addition, three K-ras alleles, designated as susceptible (Ks), intermediate (Ki), or resistant (Kr), were identified by sequence analysis of the second intron of the K-ras gene from 32 strains of mice. These K-ras alleles are associated with differences in mouse lung tumor susceptibility. All Kralleles have a tandem 37-bp direct repeat (nt 282-355) in the second intron of the K-ras gene. Ksand Kialleles have only one copy of the 37-bp sequence (nt 282-318). Ksstrains have three base variations at nt 288, 296, and 494, and Kistrains have two base variations at nt 288 and 494 in the second intron of the K-ras gene. Differential protein-binding patterns were observed in gel-mobility-shift experiments between the duplicated 37-bp sequence of the Krallele and the single 37-bp sequence of the Ksand Kialleles. DNase I footprinting assay revealed protein binding sites in the second intron of the K-ras gene that correspond to the tandem repeat sequences. Our data suggest that higher expression of the A/J allele relative to C3H allele may be responsible for the allele-specific activation of the K-ras gene in lung tumors from F1hybrid mice.