Adrenocorticotropin/3',5'-cyclic AMP-mediated transcription of the scavenger akr1-b7 gene in adrenocortical cells is dependent on three functionally distinct steroidogenic factor-1-responsive elements

Endocrinology. 2004 Feb;145(2):508-18. doi: 10.1210/en.2003-1093. Epub 2003 Nov 6.

Abstract

The akr1-b7 gene encodes a scavenger enzyme expressed in steroidogenic glands under pituitary control. In the zona fasciculata of the adrenal cortex where its expression is controlled by ACTH, AKR1-B7 detoxifies isocaproaldehyde produced during the first step of steroidogenesis. Three steroidogenic factor-1 (SF-1)-responsive elements (SFREs) are contained within the -510/+41 promoter region, which was previously demonstrated to drive gene expression in transgenic mice adrenal cortex. All these sequences bind at least SF-1 in Y1 adrenocortical cell nuclear extracts and can be activated by overexpression of this factor in HeLa cells. However, the three SFREs show distinct properties regarding akr1-b7 promoter activity in Y1 cells. Whereas the proximal -102 SFRE supports basal promoter activity, the -458 bona fide SFRE is essential for both basal promoter activity and cAMP responsiveness, although it is unresponsive to cAMP when isolated from its promoter context. This suggests that SF-1 is not a cAMP-responsive factor per se. The neighboring SFRE at -503 is a palindromic sequence that binds monomeric and heteromeric SF-1 as well as an adrenal-specific complex. Using MA-10 Leydig cells and Y1-10r9 mutant cells, we provide evidence that its activity in adrenocortical cells depends on the binding of the adrenal-specific factor, which is required for basal and cAMP-induced promoter activity. Furthermore, the -503 site has intrinsic cAMP-sensing ability in Y1 cells, which is correlated with increased adrenal-specific complex binding. Collectively, our results suggest that cAMP responsiveness of the akr1-b7 promoter is achieved through cooperation between the adrenal-specific factor bound to the -503 site and SF-1 bound to the -458 site.

MeSH terms

  • Adrenal Cortex / metabolism*
  • Adrenocorticotropic Hormone / physiology*
  • Aldehyde Reductase*
  • Animals
  • Base Sequence
  • Binding Sites / genetics
  • Cell Line
  • Cell Nucleus / chemistry
  • Colforsin / pharmacology
  • Cyclic AMP / physiology*
  • DNA / chemistry
  • DNA / metabolism
  • DNA-Binding Proteins / metabolism*
  • Fushi Tarazu Transcription Factors
  • HeLa Cells
  • Homeodomain Proteins
  • Humans
  • Mice
  • Mutagenesis
  • Promoter Regions, Genetic / genetics
  • Proteins / genetics*
  • Receptors, Cytoplasmic and Nuclear
  • Response Elements / genetics*
  • Steroidogenic Factor 1
  • Transcription Factors / metabolism*
  • Transcription, Genetic*
  • Transcriptional Activation
  • Transfection

Substances

  • DNA-Binding Proteins
  • Fushi Tarazu Transcription Factors
  • Homeodomain Proteins
  • NR5A1 protein, human
  • Proteins
  • Receptors, Cytoplasmic and Nuclear
  • Steroidogenic Factor 1
  • Transcription Factors
  • steroidogenic factor 1, mouse
  • Colforsin
  • Adrenocorticotropic Hormone
  • DNA
  • Cyclic AMP
  • Akr1b7 protein, mouse
  • Aldehyde Reductase