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5-azaC treatment enhances expression of transforming growth factor-beta receptors through down-regulation of Sp3

S Ammanamanchi1, M G Brattain

  • 1Department of Surgery, The University of Texas Health Science Center, San Antonio, Texas 78229, USA.

The Journal of Biological Chemistry
|July 10, 2001
PubMed

Insights

5-aza cytidine (5-azaC) treatment down-regulates Sp3, a transcriptional repressor, leading to increased expression of transforming growth factor-beta receptors type I (RI) and type II (RII) in cancer cells.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Epigenetics

Background:

  • Sp3 functions as a transcriptional repressor for transforming growth factor-beta receptors type I (RI) and type II (RII).
  • Epigenetic modifications, such as DNA methylation, can influence gene expression and protein activity.

Purpose of the Study:

  • To investigate the effect of 5-aza cytidine (5-azaC) on Sp3 expression and its subsequent impact on RI and RII receptor levels in cancer cells.
  • To elucidate the molecular mechanisms underlying 5-azaC-mediated regulation of Sp3, RI, and RII.

Main Methods:

  • Western blot analysis to assess protein levels of Sp3, RI, and RII.
  • Gel shift and Southwestern analyses to evaluate Sp3 DNA-binding activity to Sp1 consensus sequences and RI/RII promoters.
  • Reverse transcription-polymerase chain reaction (RT-PCR) and nuclear run-on assays to determine Sp3 mRNA levels and transcription rates.

Main Results:

  • 5-azaC treatment reduced Sp3 protein levels and its binding affinity to RI and RII promoters in MCF-7L breast and GEO colon cancer cells.
  • Decreased Sp3 mRNA levels and transcription were observed following 5-azaC treatment, indicating transcriptional down-regulation of Sp3.
  • Concomitant induction of RI and RII expression was observed, correlating with reduced Sp3 binding and activity.

Conclusions:

  • 5-azaC treatment down-regulates Sp3 expression and activity, leading to the de-repression and subsequent induction of transforming growth factor-beta receptors RI and RII.
  • The effects of 5-azaC on RI and RII expression involve a dual mechanism affecting both Sp1 and Sp3 transcription factors.
  • These findings highlight the role of epigenetic regulation by 5-azaC in modulating key signaling pathways relevant to cancer progression.

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