Pituitary Homeobox Factor 1, A Novel Transcription Factor in the Adrenal Regulating Steroid 11ß-hydroxylase

N. Hiroi; T. Kino; M. Bassett; W. E. Rainey; M. Phung; M. Abu-Asab; T. Fojo; P. Briata; G. P. Chrousos; S. R. Bornstein

doi:10.1055/s-2003-41301

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2003; 35(5): 273-278
DOI: 10.1055/s-2003-41301

Original Basic

Pituitary Homeobox Factor 1, A Novel Transcription Factor in the Adrenal Regulating Steroid 11ß-hydroxylase

N. Hiroi ^1, ⁴ , T. Kino ¹ , M. Bassett ⁵ , W. E. Rainey ⁵ , M. Phung ¹ , M. Abu-Asab ² , T. Fojo ³ , P. Briata ^6, ⁷ , G. P. Chrousos ¹ , S. R. Bornstein ^1, ⁴

¹ Pediatric and Reproductive Endocrinology Branch, National Institute of Child Health and Human Development
² Laboratory of Pathology
³ Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
⁴ Department of Endocrinology, Heinrich Heine University of Düsseldorf, Germany
⁵ Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
⁶ School and Department of Medicine, Howard Hughes Medical Institute, University of California, San Diego, La Jolla California, USA
⁷ Istituto Nazionale Per La Ricerca Suc Cancro, Genova, Italy

This work was presented in part at the 84th annual meeting of the Endocrine Society.

Abstract

Pituitary homeobox 1 (Ptx1/Pitx1) is a homeodomain-containing transcription factor present throughout pituitary development. Ptx1/Pitx1 interacts with steroidogenic factor 1 (SF-1) in the regulation of pituitary gene expression. SF-1 also plays a critical role in the transcription of enzymes involved in adrenal steroidogenesis. Therefore, we analyzed the presence and role of Ptx1/Pitx1 in human adrenal cortex. Both Ptx1/Pitx1 and SF-1 mRNA were expressed in the human adrenal gland, and immuno-electron microscopy demonstrated the presence of Ptx1/Pitx1 protein in the nucleus of adrenocortical cells. Computer analysis revealed the presence of Ptx1/Pitx1 signal sequences within the promoter region of human 11β hydroxylase (hCYP11B1). To examine the role of Ptx1/Pitx1 in the regulation of the genes, we prepared reporter constructs using the 5’-flanking DNA of the hCYP11B1 gene and transfected them into Y-1 mouse adrenocortical cells, HeLa and CV-1 cells. Ptx1/Pitx1 stimulation of hCYP11B1 reporter activity (3-fold over basal) in Y-1 cells was equal to that observed with SF-1. The hCYP11B1 promoter activity in Y-1 cells was not synergistically increased by co-transfection with both Ptx1/Pitx1 and SF-1. Both basal and ACTH-stimulated hCYP11B1 reporter activities in Y-1 cells were increased by co-transfection with either Ptx1/Pitx1 or SF-1 expression vectors. In contrast, co-transfection with both Ptx1/Pitx1 and SF-1 synergistically increased hCYP11B1 promoter activity in HeLa and CV-1 cells (5-fold and 20-fold over basal, respectively). In conclusion, this study represents the first demonstration for a role of Ptx1/Pitx1 in the regulation of transcription of enzymes involved in adrenal steroidogenesis.

Key words

Pituitary Homeobox Factor 1 Ptx1/Pitx1 - 11β-hydroxylase - Steroidogenic Factor 1 (SF-1)

Full Text

References

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N. Hiroi, M. D.

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