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Oncogenic Ras upregulates NADPH oxidase 1 gene expression through MEK-ERK-dependent phosphorylation of GATA-6

Y Adachi1, Y Shibai, J Mitsushita

  • 1Department of Molecular Biology and Biochemistry, Shinshu University School of Medicine, Nagano, Japan.

Oncogene
|May 6, 2008
PubMed

Insights

Oncogenic Ras signaling boosts nicotinamide adenine dinucleotide phosphate oxidase (Nox) 1 expression in colon cancer cells. This occurs through MEK-ERK-dependent phosphorylation of GATA-6, a transcription factor that binds to the Nox1 promoter, driving cancer cell growth.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Oncology

Background:

  • Ras oncogenes are critical drivers of cancer, promoting cell proliferation and survival.
  • Nicotinamide adenine dinucleotide phosphate oxidase (Nox) 1 is upregulated by Ras signaling, contributing to reactive oxygen species production and cancer phenotypes.
  • The precise transcriptional regulation of Ras-induced Nox1 expression is not fully understood.

Purpose of the Study:

  • To elucidate the transcriptional control mechanism of Ras-induced Nox1 expression.
  • To identify the specific transcription factors and signaling pathways involved in Nox1 gene regulation.

Main Methods:

  • Analysis of the Nox1 promoter activity in colon cancer cells (CaCo-2).
  • Chromatin immunoprecipitation (ChIP) and supershift assays to identify protein-DNA interactions.
  • Site-directed mutagenesis to investigate the role of GATA-6 phosphorylation.
  • Inhibition of the MEK/ERK pathway using PD98059.

Main Results:

  • Ras signaling enhances Nox1 promoter activity via the MEK/ERK pathway.
  • GATA-6 binds to specific sites on the Nox1 promoter and trans-activates its transcription.
  • MEK-activated ERK phosphorylates GATA-6 at serine residues, increasing its DNA binding affinity.
  • Mutation of the ERK phosphorylation site on GATA-6 abolishes its trans-activation activity and suppresses colon cancer cell growth.

Conclusions:

  • Oncogenic Ras signaling upregulates Nox1 transcription through MEK-ERK-dependent phosphorylation of GATA-6.
  • This pathway is crucial for maintaining Ras-transformation phenotypes and driving colon cancer cell proliferation.
  • GATA-6 is a key mediator linking Ras signaling to Nox1 expression and cancer progression.

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