Characterization of a novel hexameric repeat DNA sequence in the promoter of the immediate early gene, IEX-1, that mediates 1α, 25-dihydroxyvitamin D3-associated IEX-1 gene repression

Hee Jeong Im, Theodore A. Craig, Mark R. Pittelkow, Rajiv Kumar

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

1α, 25-Dihydroxyvitamin D3(1α, 25(OH)2D3), the active metabolite of vitamin D3, mediates anti-proliferative effects in cells by regulating the expression of 1α, 25(OH)2D3-responsive genes. The expression of the proliferation-promoting Immediate Early gene X-1 (IEX-1) is reduced by 1α, 25(OH)2D3 through unknown mechanisms. Here we report the presence of a novel inhibitory hexameric repeat DNA response element in the promoter of the human IEX-1 gene that mediates 1α, 25(OH)2D3-associated IEX-1 gene repression. To localize a vitamin D sensitive DNA response element we transfected the keratinocyte-like cell line, HaCaT, (referred as HaCaT) with a series of plasmids containing full-length and truncated IEX-1 promoter elements fused to the luciferase reporter gene in the absence or presence of 1α, 25(OH)2D3, and we performed electrophoretic gel mobility assays in the presence of receptors for 1α, 25(OH)2D3 (vitamin D receptor, VDR) and 9-cis-retinoic acid (RXRα). We mapped a negative response element between nt -405 and -391(15 bp) of the IEX-1 promoter (5′-TGAACC AGG GAGTCA-3′) that mediates transcriptional inhibition in response to 1α, 25(OH)2D3 and which requires expression of both nuclear receptors for 1α, 25(OH)2D3 and 9-cis-retinoic acid. Our data indicate that the physiological repression of IEX-1 gene expression by 1α, 25(OH)2D3 is directly mediated by nuclear VDR/RXRα heterodimers through a specific transcriptional element.

Original languageEnglish (US)
Pages (from-to)3706-3714
Number of pages9
JournalOncogene
Volume21
Issue number23
DOIs
StatePublished - May 23 2002

Keywords

  • IEX-I
  • Immediate early gene
  • Transcriptional suppression
  • VDRE

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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