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Involvement of serum response element in okadaic acid-induced EGR-1 transcription in human T-cells

D Chauhan1, S M Kharbanda, H Uchiyama

  • 1Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.

Cancer Research
|April 15, 1994
PubMed

Insights

Okadaic acid transiently induces EGR-1 gene expression in T-cells, primarily through transcriptional regulation. This process involves the CArG element, suggesting protein phosphatases PP-1 and PP-2A

Area of Science:

  • Molecular Biology
  • Immunology
  • Cell Signaling

Background:

  • Serine/threonine protein phosphatases PP-1 and PP-2A are crucial regulators of cellular processes.
  • Early growth response gene-1 (EGR-1) is a transcription factor involved in T-cell activation.
  • Okadaic acid is a specific inhibitor of PP-1 and PP-2A.

Purpose of the Study:

  • To investigate the effect of okadaic acid on EGR-1 gene expression in T-cells.
  • To elucidate the regulatory mechanisms of EGR-1 gene expression induced by okadaic acid.
  • To determine the role of PP-1 and PP-2A in T-cell activation via EGR-1 regulation.

Main Methods:

  • Treatment of normal peripheral blood T-cells and Jurkat cells with okadaic acid.
  • Analysis of EGR-1 mRNA levels using Northern blotting and nuclear run-on assays.
  • Reporter gene assays using chloramphenicol acetyltransferase (CAT) to assess promoter activity.
  • Site-directed mutagenesis of the CArG element in the EGR-1 promoter.

Main Results:

  • Okadaic acid caused a transient induction of EGR-1 gene expression, peaking at 3-6 hours.
  • EGR-1 mRNA levels were superinduced by okadaic acid combined with cycloheximide, indicating post-transcriptional regulation.
  • Nuclear run-on assays confirmed transcriptional control of EGR-1 induction by okadaic acid.
  • The 5' most distal CArG box in the EGR-1 promoter was identified as essential for okadaic acid-induced transcription.

Conclusions:

  • Okadaic acid regulates EGR-1 gene expression at the transcriptional level.
  • The CArG element within the EGR-1 promoter mediates the transcriptional response to okadaic acid.
  • Protein phosphatases PP-1 and PP-2A likely play a significant role in T-cell activation through EGR-1 regulation.

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