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.
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.
Val
Pierre
P
Unité Mixte de Recherche Centre National de la Recherche Scientifique, 6547 Physiologie Comparée et Endocrinologie Moléculaire, Université Blaise Pascal, Clermont II, Complexe Universitaire des Cézeaux, 24 avenue des Landais, 63177 Aubière cedex, France.
Aigueperse
Christelle
C
Ragazzon
Bruno
B
Veyssière
Georges
G
Lefrançois-Martinez
Anne-Marie
AM
Martinez
Antoine
A
D000302:Adrenal Cortex / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000502:physiology*; D000449:Aldehyde Reductase; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051717:Fushi Tarazu Transcription Factors; D006367:HeLa Cells; D018398:Homeodomain Proteins; D006801:Humans; D051379:Mice; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000235:genetics; D011506:Proteins / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear; D020218:Response Elements / Q000235:genetics*; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse; D005576:Colforsin; D000324:Adrenocorticotropic Hormone; D004247:DNA; D000242:Cyclic AMP; C066498:Akr1b7 protein, mouse; D000449:Aldehyde Reductase