Transcriptional complexes at the CYP17 CRS.
Steroid hormone biosynthesis in the adrenal cortex is controlled by the peptide hormone adrenocorticotropin (ACTH), which acts to increase intracellular cAMP, resulting in the activation of cAMP-dependent protein kinase (PKA) and subsequent increase in steroidogenic gene transcription. We have identified three proteins interacting with the human CYP17 cAMP responsive sequence (CRS): steroidogenic factor 1 (SF-1), p54nrb, and polypyrimidine tract-binding protein-associated splicing factor (PSF). Nuclear extracts isolated from cAMP stimulated of H295R cells showed cAMP-inducible binding to the human CYP17 (hCYP17) CRS. This cAMP-inducible binding was dependent on a dual-specificity phosphatase (DSP). DSP activity was subsequently shown to be is essential for conveying ACTH/cAMP-stimulated transcription of several steroidogenic genes in the human adrenal cortex. We report here that the transactivation potential of SF-1 is also dependent on phosphatase activity; suggesting that SF-1 is dephosphorylated in response to ACTH/cAMP stimulation. Finally, we demonstrate a role for mitogen-activated protein kinase phosphatase 1 (MKP-1), a nuclear DSP, in conveying SF-1-dependent transcription of an hCYP17 promoter-reporter construct in the H295R human adrenocortical cell line. We conclude that a DSP, possibly MKP-1, is essential for enhancing hCYP17 transcription in the adrenal cortex by desphosphorylating of SF-1, thereby increasing the binding affinity of SF-1, p54nrb, and PSF for the hCYP17 promoter.
Sewer
M B
MB
School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA. marion@toxicology.mc.vanderbilt.edu
Waterman
M R
MR
D018797:Cell Cycle Proteins; D000242:Cyclic AMP / Q000235:genetics*; D054638:Dual Specificity Phosphatase 1; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D017874:Immediate-Early Proteins / Q000502:physiology; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000502:physiology; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured
C464455:CYYR1 protein, human; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D011506:Proteins; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D010744:Phosphoric Monoester Hydrolases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases