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Updated: Nov 3, 2025

Studying TGF-β Signaling and TGF-β-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells
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Nuclear Respiratory Factor-1, a Novel SMAD4 Binding Protein, Represses TGF-β/SMAD4 Signaling by Functioning as a

Nirmal Rajasekaran1, Kyoung Song2, Jin-Hee Lee1

  • 1Laboratory of Molecular Pathology and Cancer Genomics, Research Institute of Pharmaceutical Sciences and College of Pharmacy, Seoul National University, Seoul 08826, Korea.

International Journal of Molecular Sciences
|June 2, 2021
PubMed

Insights

Nuclear respiratory factor-1 (NRF1) inhibits tumor suppressor pathways by interacting with SMAD4. NRF1 also decreases SMAD4 expression, impacting cancer progression and TGF-β signaling.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Signaling

Background:

  • SMAD4 is crucial for transforming growth factor-β (TGF-β) signaling, regulating cell growth, migration, and apoptosis.
  • TGF-β/SMAD4 signaling typically induces growth arrest via target genes like p21WAF1 and p15INK4b.
  • SMAD4 mutations or deletions are linked to tumorigenesis, but some cancers lack these genetic alterations.

Purpose of the Study:

  • To investigate how TGF-β signaling contributes to cancer despite intact SMAD4 function.
  • To identify novel regulators of SMAD4 that may influence its tumor suppressive role.
  • To elucidate the molecular mechanisms underlying SMAD4 pathway dysregulation in cancer.

Main Methods:

  • Co-immunoprecipitation assays to identify SMAD4 interacting partners.
  • Quantitative real-time PCR (qRT-PCR) to measure mRNA expression levels.
  • Chromatin immunoprecipitation (ChIP) assays to assess promoter binding.

Main Results:

  • Nuclear respiratory factor-1 (NRF1) was identified as a novel binding partner of SMAD4.
  • NRF1 inhibits TGF-β/SMAD4-induced p15INK4b mRNA expression by binding to SMAD4.
  • NRF1 directly binds to the SMAD4 promoter, reducing SMAD4 mRNA expression.

Conclusions:

  • NRF1 acts as a negative regulator of SMAD4.
  • NRF1 interferes with TGF-β/SMAD-induced tumor suppression, potentially promoting tumorigenesis.
  • These findings offer new insights into SMAD4 signaling suppression in cancer development.
Keywords:
NRF1SMAD4p15INK4btransforming growth factor-βtumor suppression

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