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Updated: Aug 7, 2026

Inducible and Reversible Dominant-negative (DN) Protein Inhibition
08:35

Inducible and Reversible Dominant-negative (DN) Protein Inhibition

Published on: January 7, 2019

A dominant-negative mutant of raf blocks mitogen-activated protein kinase activation by growth factors and oncogenic

D Schaap1, J van der Wal, L R Howe

  • 1Division of Cellular Biochemistry, The Netherlands Cancer Institute, Amsterdam.

The Journal of Biological Chemistry
|September 25, 1993
PubMed

Insights

The serine/threonine kinase p74raf-1 is crucial for mitogen-activated protein kinase kinase activation. Its N-terminal domain acts as a competitive inhibitor, blocking extracellular signal-regulated kinase 2 (ERK2) activation.

Area of Science:

  • Cell signaling
  • Molecular biology
  • Kinase regulation

Background:

  • p74raf-1, a serine/threonine kinase, is structurally similar to protein kinase C (PKC) and possesses a regulatory N-terminal cysteine motif.
  • p74raf-1 acts upstream of mitogen-activated protein (MAP) kinase kinase in signaling pathways.

Purpose of the Study:

  • To investigate the role of the N-terminal regulatory domain of p74raf-1 in MAP kinase kinase activation.
  • To determine if p74raf-1 is essential for epidermal growth factor (EGF) and phorbol ester-induced extracellular signal-regulated kinase 2 (ERK2) activation.

Main Methods:

  • Constructed a p74raf-1 mutant (N delta raf) containing only the N-terminal regulatory domain.
  • Expressed N delta raf in COS-M6 cells and assessed its effect on ERK2 activation induced by various stimuli.
  • Investigated the effect of overexpressing full-length p74raf-1 and different PKC isoforms in cells expressing N delta raf.

Main Results:

  • N delta raf expression inhibited ERK2 activation induced by EGF, phorbol ester, serum, and oncogenic p21ras.
  • Constructs with cysteine motifs from PKC-alpha or diacylglycerol kinase did not inhibit ERK2 activation.
  • Overexpression of full-length p74raf-1 rescued N delta raf-induced inhibition of ERK2, suggesting competitive inhibition.
  • Overexpression of PKC-alpha, -epsilon, or -zeta could not rescue ERK2 inhibition.

Conclusions:

  • p74raf-1 is an essential mediator of EGF- and phorbol ester-induced ERK2 activation.
  • The MAP kinase kinase activity of p74raf-1 is not functionally substitutable by PKC-alpha, -epsilon, or -zeta.

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