Pituitary homeobox factor 1, a novel transcription factor in the adrenal regulating steroid 11beta-hydroxylase.
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 11beta 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.
Hiroi
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N
Pediatric and Reproductive Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA. n-hiroi@tkf.att.ne.jp
Kino
T
T
Bassett
M
M
Rainey
W E
WE
Phung
M
M
Abu-Asab
M
M
Fojo
T
T
Briata
P
P
Chrousos
G P
GP
Bornstein
S R
SR
D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics; D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D051761:Paired Box Transcription Factors; D010902:Pituitary Gland / Q000378:metabolism*; D017354:Point Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013252:Steroid 11-beta-Hydroxylase / Q000096:biosynthesis* / Q000235:genetics; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000235:genetics*
D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D051761:Paired Box Transcription Factors; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C101485:homeobox protein PITX1; C515058:steroidogenic factor 1, mouse; D008156:Luciferases; D013252:Steroid 11-beta-Hydroxylase