Identification of radicicol as an inhibitor of in vivo Ras/Raf interaction with the yeast two-hybrid screening system

Se Won Ki, Koji Kasahara, Ho Jeong Kwon, Jun Eishima, Kazutoh Takesako, Jonathan A. Cooper, Minoru Yoshida, Sueharu Horinouchi

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19 Citations (Scopus)


Activation of cytoplasmic serine/threonine kinase Raf-1, an important effector of Ras, requires direct binding to Ras. The yeast two-hybrid screening system used for identification of inhibitors of Ras/Raf-1 interaction showed radicicol to be an inhibitor. Radicicol has been shown to induce morphological reversion of transformed cells. Immunoprecipitation with an anti-Ras antibody revealed that the in vivo Ras/Raf-1 binding in v-Ha-ras-transformed cells was also blocked by low concentrations of radicicol (0.1 ~ 1 μg/ml), while degradation of Raf-1 was induced at concentrations higher than 2 μg/ml. However, in vitro binding of glutathion S-transferase-fused Ras to a maltose binding protein-fused RIP3 containing the Ras-binding domain (RBD) of Raf-1 was not inhibited by radicicol. Similar two-hybrid assays with several truncated forms of Raf-1 showed that both the conserved serine/threonine-rich domain (CR2) and the C-terminal protein kinase domain (CR3) were required for the full inhibition by radicicol. These results suggest that radicicol interacts directly or indirectly with the region except with RBD of Raf-1, thereby inhibiting a conformational change of Raf-1 prerequisite for binding to Ras.

Original languageEnglish
Pages (from-to)936-944
Number of pages9
JournalJournal of Antibiotics
Issue number10
Publication statusPublished - 1998 Oct

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Drug Discovery


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