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C/EBPalpha inhibits cell growth via direct repression of E2F-DP-mediated transcription

B A Slomiany1, K L D'Arigo, M M Kelly

  • 1Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.

Molecular and Cellular Biology
|July 27, 2000
PubMed

Insights

The transcription factor C/EBPalpha inhibits cell division in mouse cells by blocking the transcription of genes essential for cell proliferation. This antimitogenic effect is mediated by repressing E2F-DP-driven S-phase gene expression.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Gene Regulation

Background:

  • CCAAT/enhancer-binding proteins (C/EBPs) are transcription factors regulating cell differentiation and metabolism.
  • The role of C/EBPalpha in cell cycle control is not fully understood.
  • Understanding C/EBPalpha's function is crucial for comprehending cell growth regulation.

Purpose of the Study:

  • To investigate the antimitogenic effects of C/EBPalpha in mouse cell lines.
  • To elucidate the molecular mechanism by which C/EBPalpha inhibits cell division.
  • To determine if C/EBPalpha interacts with cell cycle regulatory proteins.

Main Methods:

  • Utilized an inducible transcription system for regulated C/EBPalpha expression in L and NIH 3T3 cells.
  • Performed chromatin immunoprecipitation assays to detect protein-DNA interactions.
  • Conducted transient-transfection assays with reporter genes to assess promoter activity.
  • Analyzed protein complexes using nuclear extracts and recombinant proteins.

Main Results:

  • Ectopic expression of C/EBPalpha significantly inhibited cell division in mouse cells, an effect not reversed by viral oncoproteins.
  • C/EBPalpha formed a complex that bound to E2F binding sites in the promoters of E2F-1 and dihydrofolate reductase (DHFR) genes.
  • Bacterially expressed C/EBPalpha alone did not bind E2F sites, but its addition to nuclear extracts induced E2F binding activity containing C/EBPalpha.
  • C/EBPalpha directly inhibited E2F-DP1-mediated promoter induction and S-phase gene transcription.

Conclusions:

  • C/EBPalpha acts as a potent antimitogen by directly repressing E2F-DP-mediated transcription of S-phase genes.
  • This mechanism provides a straightforward pathway for C/EBPalpha-induced cell growth arrest.
  • The findings highlight C/EBPalpha's critical role in regulating the cell cycle through transcriptional repression.

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