Divergent regulation of the growth-promoting gene IEX-1 by the p53 tumor suppressor and Sp1

Hee Jeong Im, Mark R. Pittelkow, Rajiv Kumar

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


IEX-1, a recently discovered early response gene, regulates cell growth and apoptosis. IEX-1 gene expression is regulated by a variety of factors such as x-irradiation, ultraviolet radiation, steroids, growth factors, and inflammatory stimuli. By systematic examination of the IEX-1 promoter, we show that IEX-1 gene expression is controlled by multiple conserved gene regulatory elements and that IEX-1 is a downstream target of the p53 tumor suppressor and Sp1. In addition, p300, Sox, nuclear factor-κB, and AP4 appear to be modulators of IEX-1 gene expression to a lesser degree. We found that there is at least one Sp1 element that functions as an activator and contributes to high basal transcriptional levels of the IEX-1 gene. We demonstrate the presence of a p53 response element that represses IEX-1 promoter activity in HaCaT keratinocytes, indicating that Sp1 and p53 have opposite effects on IEX-1 gene expression. We conclude that IEX-1 expression in cells is regulated by the p53 tumor suppressor and Sp1, thus providing a direct mechanism for control of cell proliferation.

Original languageEnglish (US)
Pages (from-to)14612-14621
Number of pages10
JournalJournal of Biological Chemistry
Issue number17
StatePublished - Apr 26 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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