Resistance of K-RasBV12 proteins to farnesyltransferase inhibitors in Rat1 cells

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Benzodiazepine (BZA)-5B, a CAAX farnesyltransferase inhibitor, was previously shown to block the farnesylation of H-Ras and to reverse the transformed morphology of Rat1 cells expressing oncogenic H-RasV12. Nontransformed Rat1 cells were not affected by BZA-5B, suggesting that they produce a form of Ras whose prenylation is not blocked by this compound. The likely candidate is K-RasB, which differs from H-Ras primarily in the terminal 24 amino acids. In the current study we examined the effect of BZA-5B on the prenylation of a chimeric oncogenic Ras protein designated H/K-RasBV12, consisting of the first 164 amino acids of H-RasV12 followed by the last 24 amino acids of K-RasB. BZA-5B failed to block the prenylation of this chimera and was thus unable to reverse the transformed morphology of Rat1 cells in which it was expressed. Another potent inhibitor of H-Ras farnesylation, L-739,749, also failed to block prenylation of H/K-RasBV12. Similar results were obtained in transfected cells expressing a widely used version of K-RasBV12 containing a 10-amino acid extension at its NH2 terminus. Neither BZA-5B nor L-739,749 reversed the transformed morphology of cells expressing H/K-RasBV12. The resistance of K-RasB to farnesyltransferase inhibition provides a likely explanation for the resistance of nontransformed cells to the growth inhibitory effects of BZA-5B and L-739,749.

Original languageEnglish (US)
Pages (from-to)4454-4458
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number9
StatePublished - Apr 30 1996


  • Benzodiazepine-5B
  • Geranylgeranyl transferase I
  • L-739,749
  • Protein prenylation
  • Transformed cells

ASJC Scopus subject areas

  • General


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