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A structural basis for mutational inactivation of the tumour suppressor Smad4

Y Shi1, A Hata, R S Lo

  • 1Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.

Nature
|July 3, 1997
PubMed

Insights

The Smad4/DPC4 tumor suppressor

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Structural Biology

Background:

  • Smad4/DPC4 is a crucial tumor suppressor gene inactivated in pancreatic cancer and other malignancies.
  • Smad proteins mediate signaling pathways for the TGF-beta cytokine superfamily.
  • Smad4/DPC4 is essential for hetero-oligomerization among SMAD proteins, playing a central role in signal transduction.

Purpose of the Study:

  • To determine the crystal structure of the C-terminal domain (CTD) of the Smad4/DPC4 tumor suppressor.
  • To elucidate the structural basis for Smad4/DPC4 function and its inactivation in cancer.

Main Methods:

  • X-ray crystallography at 2.5 A resolution to determine the structure of the Smad4/DPC4 CTD.
  • Analysis of tumor-derived missense mutations in relation to the determined structure.

Main Results:

  • The Smad4/DPC4 CTD forms a stable crystallographic trimer via a conserved protein-protein interface.
  • The majority of cancer-associated missense mutations map to this trimeric interface.
  • These mutations were shown to disrupt Smad4/DPC4 homo-oligomerization both in vitro and in vivo.

Conclusions:

  • The trimeric assembly of the Smad4/DPC4 CTD is critical for its signaling function.
  • Tumorigenic mutations in Smad4/DPC4 disrupt this essential trimeric structure, leading to impaired signaling.
  • Understanding this structural mechanism provides insights into pancreatic cancer development.

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