HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 30, 22052-22061, July 27, 2007

This Article Full Text Full Text (PDF) All Versions of this Article: 282/30/22052    most recent M702614200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Xing, W. Articles by Mohan, S. Search for Related Content PubMed PubMed Citation Articles by Xing, W. Articles by Mohan, S. Social Bookmarking                      What's this?

Nuclear Factor-E2-related Factor-1 Mediates Ascorbic Acid Induction of Osterix Expression via Interaction with Antioxidant-Responsive Element in Bone Cells^*

Weirong Xing, Anny Singgih, Anil Kapoor, Catrina M. Alarcon, David J. Baylink, and Subburaman Mohan¹

From the Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Affairs Medical Center, Loma Linda, California 92357 and the Department of Medicine, Loma Linda University, Loma Linda, California 92357

We recently found that deletion of the gulonolactone oxidase gene, which is involved in the synthesis of ascorbic acid (AA), was responsible for the fracture phenotype in spontaneous fracture mice. To explore the molecular mechanisms by which AA regulates osteoblast differentiation, we examined the effect of AA on osterix expression via Nrf1 (NF-E2-related factor-1) binding to antioxidant-responsive element (ARE) in bone marrow stromal (BMS) cells. AA treatment caused a 6-fold increase in osterix expression in mutant BMS cells at 24 h, which was unaffected by pretreatment with protein synthesis inhibitor. Sequence analyses of mouse osterix promoter revealed a putative ARE located at -1762 to -1733 upstream of the transcription start site to which Nrf potentially binds. A gel mobility shift assay revealed that nuclear proteins from AA-treated BMS cells bound to radiolabeled ARE much more strongly than nuclear extracts from AA-untreated cells. A chromatin immunoprecipitation assay with Nrf1 antibody confirmed the interaction of Nrf1 with the mouse osterix promoter. A reporter assay demonstrated that the promoter activity of mouse osterix containing an ARE was stimulated 4-fold by a 48-h treatment with AA in spontaneous fracture BMS cells. Treatment of mutant BMS cells with AA resulted in a 3.9-fold increase in the nuclear accumulation of Nrf1. Transfection of mutant BMS cells with Nrf1 small interfering RNA decreased Nrf1 protein by 4.5-fold, blocked AA induction of osterix expression, and impaired BMS cell differentiation. Our data provided the first experimental evidence that AA modulated osterix expression via a novel mechanism involving Nrf1 nuclear translocation and Nrf1 binding to ARE to activate genes critical for cell differentiation.

Received for publication, March 27, 2007

^* This work was supported by National Institutes of Health Grant AG19698 and the Department of Veterans Affairs. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Musculoskeletal Disease Center, Jerry L. Pettis Memorial Veterans Administration Medical Center, Loma Linda, CA 92357. Tel.: 909-825-7084 (ext. 2932); Fax: 909-796-1680; E-mail: Subburaman.Mohan{at}va.gov.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?