This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ricketts, M H Articles by Levinson, A D Search for Related Content PubMed PubMed Citation Articles by Ricketts, M H Articles by Levinson, A D

 Previous Article  |  Next Article 

Mol Cell Biol. 1988 April; 8(4): 1460-1468

High-level expression of c-H-ras1 fails to fully transform rat-1 cells.

Department of Cell Genetics, Genetech Inc., South San Francisco, California 94080.

ABSTRACT

Rat-1 cells were transfected with plasmids encoding normal (Gly-12), nonactivated (Pro-12), and activated (Val-12 and Ile-12) p21H-ras in the presence of an amplifiable dihydrofolate reductase marker. The introduced DNA was amplified by selection in methotrexate to establish the relationship between p21H-ras expression and various hallmarks of cellular transformation. The maximum level of p21H-ras (Gly-12) consistent with cell viability was approximately 0.13% of total cell protein (approximately 60,000 molecules per cell); this is 44-fold greater than the level of the endogenous protein. The maximum tolerated level of a second nontransforming form of p21H-ras (pro-12) was about half of this. Amplification in Rat-1 cells of H-ras genes encoding the highly oncogenic Val-12 and Ile-12 forms of p21H-ras could not be achieved by methotrexate selection, providing strong evidence that synthesis of activated p21H-ras above a certain threshold (about 0.02% of total protein) in Rat-1 cells is incompatible with cell viability. Individual cell lines were isolated and their morphology, anchorage-independent growth, tumorigenicity, and response to and production of growth factors were studied. We report that cell lines expressing near-maximum tolerated levels of either the normal or pro-12 form of p21H-ras were not as transformed as cells expressing much more modest levels of the highly oncogenic (Val-12) form, suggesting that the complete elaboration of the transformed phenotype by ras depends, at least in part, on mutations that distinguish the cellular and viral proteins. We found that cells expressing elevated levels of the normal p21(H-ras) could be fully transformed by the activated (Val-12) form and that such cells continued to overexpress p21(H-ras) (Gly-12), arguing against a role for normal ras genes in suppression of the oncogenic potential of their mutationally activated counterparts.

This article has been cited by other articles:

• Li, Q., Dang, C. V. (1999). c-Myc Overexpression Uncouples DNA Replication from Mitosis. Mol. Cell. Biol. 19: 5339-5351 [Abstract] [Full Text]  
• Finney, R., Bishop, J. (1993). Predisposition to neoplastic transformation caused by gene replacement of H-ras1. Science 260: 1524-1527 [Abstract]