Role of Raf-1 conserved region 2 in regulation of Ras-dependent Raf-1 activation

Hiroyoshi Sendoh, Chang Deng Hu, Dongmei Wu, Chunhua Song, Yuriko Yamawaki-Kataoka, Joji Kotani, Tomoyo Okada, Fumi Shima, Ken Ichi Kariya, Tohru Kataoka

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Full activation of Raf-1 requires the interaction of its CRD with Ras. The serine/threonine-rich region, CR2, of Raf-1 was implicated in Raf-1 regulation, but the underlying mechanism was unclear. Here we show that CRD loses its Ras-binding activity when expressed in connection with CR2, suggesting that CR2 masks CRD. This masking effect is abolished by substitution of Asp or Ala for Ser-259, a growth factor- and TPA-induced phosphorylation site in CR2. Treatment of COS-7 cells expressing Ha-Ras(Val-12) and Raf-1 with TPA enhances the Ha-Ras(Val-12)-dependent Raf-1 kinase activity. In contrast, the Ha-Ras(Val-12)-dependent activities of the Raf-1(S259D) and Raf-1(S259A) mutants are comparable to that of wild-type Raf-1 stimulated by both Ha-Ras(Val-12) and TPA and cannot be further stimulated by TPA treatment. These results suggest that the in vivo phosphorylation of Ser-259 may comprise a crucial step for Ras-dependent Raf-1 activation by unmasking CRD and promoting its association with Ras. (C) 2000 Academic Press.

Original languageEnglish (US)
Pages (from-to)596-602
Number of pages7
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - May 19 2000

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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