Site-specific phosphorylation of raf in cells containing oncogenic ras-p21 is likely mediated by jun-N-terminal kinase

Victor Adler, Wilbur Bowne, Josef Michl, Kelley A. Sookraj, Kamran Ikram, Sidney Pestka, Lara Izotova, Michael Zenilman, Fred K. Friedman, Yongxia Qu, Matthew R. Pincus

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In a study of interactions between the raf-MEK-MAPK (ERK) and JNK-jun pathways, we found previously that JNK can induce phosphorylation of raf but not vice versa. In this study, we investigate the nature of the JNK-induced phosphorylation of raf. In in vitro experiments in which immuno-bead-bound raf is phosphorylated by activated JNK, we find strong phosphorylation signals at raf-Ser259 and Ser338. The Ser259 phosphorylation is surprising since it is associated with inhibition of migration of raf to the cell membrane where it can interact with ras-p21. We also find that in oocytes induced to mature with oncogenic ras-p21, which induces high levels of phosphorylated JNK and MAPK, the same pattern of phosphorylation of raf occurs. In contrast, in oocytes induced to mature with insulin, which requires activation of wild-type ras-p21, phosphorylation of raf-Ser338 but not raf-Ser259 occurs. In oncogenic ras-transformed human pancreatic cancer MIA-PaCa-2 cells, phosphorylation of both raf serines occurs. Treatment of these cells with the ras peptide, PNC-2 attached to a penetratin sequence that blocks JNK and MAPK phosphorylation and induces tumor cell necrosis, results in a marked decrease in phosphorylation of raf-Ser259, but not that of raf-Ser338. These results suggest that oncogenic ras-p21 induces phosphorylation of both raf-Ser259 and Ser338 and that raf-Ser 259 phosphorylation may be effected by activated JNK.

Original languageEnglish
Pages (from-to)47-56
Number of pages10
JournalAnnals of Clinical and Laboratory Science
Issue number1
StatePublished - Dec 2008
Externally publishedYes


  • JNK
  • Oncogenic ras-p21
  • Phosphorylation
  • raf
  • raf-Ser259
  • raf-Ser338


Dive into the research topics of 'Site-specific phosphorylation of raf in cells containing oncogenic ras-p21 is likely mediated by jun-N-terminal kinase'. Together they form a unique fingerprint.

Cite this