Nuclear receptor 4A2 and C/EBPbeta regulate the parathyroid hormone-mediated transcriptional regulation of the 25-hydroxyvitamin D3-1alpha-hydroxylase.
1Alpha-hydroxylase is the enzyme responsible for the production of the active form of vitamin D, 1,25-dihydroxyvitamin D3. 1Alpha-hydroxylase, found largely in the kidney, is known to be up-regulated by parathyroid hormone (PTH), however the mechanism of action of PTH and any required transcription factors have not been clearly identified. During gene array analysis we observed that NR4A2, a nuclear orphan receptor, is markedly up-regulated in a porcine kidney cell line (AOK-B50) following PTH stimulation. NR4A2 over-expression increases the endogenous induction of 1alpha-hydroxylase mRNA in the absence of PTH, however optimal stimulation is achieved when both NR4A2 and PTH are present. An unconventional site of action of NR4A2 was localized to a fragment comprising the sequence from -35/+22 of the 1alpha-hydroxylase promoter at a C/EBP consensus site. Study of the involvement of C/EBPbeta in the 1alpha-hydroxylase regulation revealed that the transcriptional enhancement by NR4A2 on the 1alpha-hydroxylase promoter is inhibited by C/EBPbeta. In addition, C/EBPbeta over-expression decreases the endogenous levels of both NR4A2 and 1alpha-hydroxylase mRNA.
Zierold
Claudia
C
Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA.
Nehring
Jamie A
JA
DeLuca
Hector F
HF
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000201:enzymology*; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D020411:Oligonucleotide Array Sequence Analysis; D010281:Parathyroid Hormone / Q000378:metabolism* / Q000494:pharmacology; D020218:Response Elements / Q000502:physiology; D013552:Swine; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D022782:CCAAT-Enhancer-Binding Protein-beta; D004268:DNA-Binding Proteins; C539882:NR4A2 protein, human; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D010281:Parathyroid Hormone; D014157:Transcription Factors; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase