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Functional analysis of the transforming growth factor beta responsive elements in the WAF1/Cip1/p21 promoter

M B Datto1, Y Yu, X F Wang

  • 1Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA.

The Journal of Biological Chemistry
|December 1, 1995
PubMed

Insights

Transforming growth factor-beta (TGF-β) induces cell cycle arrest by increasing cyclin-dependent kinase inhibitors like p21. This study identifies a specific DNA sequence in the p21 promoter essential for TGF-β-mediated transcriptional activation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Transforming growth factor-beta (TGF-β) is a key regulator of cell proliferation and differentiation.
  • TGF-β signaling pathways are implicated in cell cycle arrest, partly through the induction of cyclin-dependent kinase inhibitors (CKIs).
  • The precise mechanisms by which TGF-β activates CKIs, such as p21/WAF1/Cip1, remain incompletely understood.

Purpose of the Study:

  • To elucidate the signaling pathways involved in TGF-β-mediated transcriptional activation of the p21 gene.
  • To identify specific DNA elements within the p21 promoter that mediate TGF-β responsiveness.
  • To characterize proteins that bind to the identified TGF-β responsive element.

Main Methods:

  • Functional analysis of the p21 promoter using deletion and mutation constructs.
  • Reporter assays to assess promoter activity under TGF-β treatment.
  • Gel shift assays to identify proteins binding to the TGF-β responsive element.

Main Results:

  • A 10-base pair sequence within the p21 promoter was identified as critical for TGF-β-induced transcriptional activation.
  • This sequence alone was sufficient to confer TGF-β responsiveness to a minimal promoter.
  • Gel shift assays revealed specific binding of transcription factors Sp-1 and Sp-3 to this TGF-β responsive element.

Conclusions:

  • The identified 10-base pair element is a key mediator of TGF-β's transcriptional control over p21 expression.
  • Sp-1 and Sp-3 are likely involved in the TGF-β signaling pathway leading to p21 transcriptional activation.
  • These findings provide initial insights into the molecular mechanisms underlying TGF-β-induced cell cycle arrest.

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