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Oct-1 transcription factor is a negative regulator of rat CYP1A1 expression via an octamer sequence in its negative

K Sterling1, E Bresnick

  • 1Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical Center, Worcester 01655, USA.

Molecular Pharmacology
|February 1, 1996
PubMed

Insights

Oct-1 binds to the rat CYP1A1 promoter's negative regulatory element, acting as a repressor. This binding significantly reduces CYP1A1 gene expression in liver cells.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Hepatology

Background:

  • The rat cytochrome P450 1A1 (CYP1A1) gene expression is tightly regulated.
  • A negative regulatory element (NRE) in the CYP1A1 promoter contains binding sites for transcription factors.

Purpose of the Study:

  • To investigate the role of the Oct-1 transcription factor in regulating rat CYP1A1 gene expression.
  • To characterize the interaction of Oct-1 with the CYP1A1 NRE.

Main Methods:

  • Gel mobility shift assays using synthesized wild-type and mutant CYP1A1 NRE sequences with nuclear extracts.
  • Reporter gene assays in transfected HepG2 cells to assess promoter activity.
  • Supershift assays with Oct-1 antibody and competition assays with Oct-1 oligodeoxyribonucleotides.

Main Results:

  • Oct-1 specifically binds to the wild-type CYP1A1 NRE, forming a major complex in nuclear extracts.
  • Mutation of the Oct-1 motif significantly reduced complex formation.
  • The wild-type NRE, but not the mutant, decreased promoter activity, an effect further enhanced by Oct-1 co-transfection.

Conclusions:

  • Oct-1 binds to the rat CYP1A1 promoter NRE.
  • Oct-1 functions as a negative regulator of rat CYP1A1 gene expression.

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