Cross-regulation between Egr-1 and APE/Ref-1 during early response to oxidative stress in the human osteoblastic HOBIT cell line: Evidence for an autoregulatory loop

Alex Pines, Nicoletta Bivi, Milena Romanello, Giuseppe Damante, Mark R. Kelley, Eileen D. Adamson, Paola D'Andrea, Franco Quadrifoglio, Luigi Moro, Gianluca Tell

Research output: Contribution to journalArticle

45 Scopus citations

Abstract

The Early Growth Response protein (Egr-1) is a C2H2-zinc finger-containing transcriptional regulator involved in the control of cell proliferation and apoptosis. Its DNA-binding activity is redox regulated in vitro through the oxidation-reduction of Cys residues within its DNA-binding domain. APE/Ref-1 is a DNA-repair enzyme with redox modulating activities on several transcription factors. In this study, by evaluating the effects of different stimuli, we found a similar timing of activation being suggestive for a common and co-linear regulation for the two proteins. Indeed, we show that APE/Ref-1 increases the Egr-1 DNA-binding activity in unstimulated osteoblastic HOBIT cells. H2O2 stimulation induces a strong interaction between Egr-1 and APE/Ref-1 at early times upon activation, as assayed by immunoprecipitation experiments. By using a cell transfection approach, we demonstrated the functional role of this interaction showing that two specific Egr-1 target genes, the PTEN phosphatase and the thymidine kinase (TK) genes promoters, are activated by contransfection of APE/Ref-1. Interestingly, by using a cell transfection approach and Chromatin immunoprecipitation assays, we were able to demonstrate that Egr-1 stimulates the transcriptional activity of APE/Ref-1 gene promoter by a direct interaction with specific DNA-binding site on its promoter. Taken together, our data delineate a new molecular mechanism of Egr-1 activation occurring soon after H2O2 stimulation in osteoblastic cells and suggest a model for a positive loop between APE/Ref-1 and Egr-1 that could explain the early transcriptional activation of APE/Ref-1 gene expression.

Original languageEnglish (US)
Pages (from-to)269-281
Number of pages13
JournalFree Radical Research
Volume39
Issue number3
DOIs
StatePublished - Mar 1 2005

Keywords

  • APE/Ref-1
  • DNA-repair
  • Egr-1
  • PKC
  • Redox regulation
  • Transcriptional regulation

ASJC Scopus subject areas

  • Biochemistry

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