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Hypoxic up-regulation of erythroid 5-aminolevulinate synthase


Hofer, T; Wenger, R H; Kramer, M F; Ferreira, G C; Gassmann, M (2003). Hypoxic up-regulation of erythroid 5-aminolevulinate synthase. Blood, 101(1):348-350.

Abstract

The erythroid-specific isoform of 5-aminolevulinate synthase (ALAS2) catalyzes the rate-limiting step in heme biosynthesis. The hypoxia-inducible factor-1 (HIF-1) transcriptionally up-regulates erythropoietin, transferrin, and transferrin receptor, leading to increased erythropoiesis and hematopoietic iron supply. To test the hypothesis that ALAS2 expression might be regulated by a similar mechanism, we exposed murine erythroleukemia cells to hypoxia (1% O(2)) and found an up to 3-fold up-regulation of ALAS2 mRNA levels and an increase in cellular heme content. A fragment of the ALAS2 promoter ranging from -716 to +1 conveyed hypoxia responsiveness to a heterologous luciferase reporter gene construct in transiently transfected HeLa cells. In contrast, iron depletion, known to induce HIF-1 activity but inhibit ALAS2 translation, did not increase ALAS2 promoter activity. Mutation of a previously predicted HIF-1-binding site (-323/-318) within this promoter fragment and DNA-binding assays revealed that hypoxic up-regulation is independent of this putative HIF-1 DNA-binding site.

The erythroid-specific isoform of 5-aminolevulinate synthase (ALAS2) catalyzes the rate-limiting step in heme biosynthesis. The hypoxia-inducible factor-1 (HIF-1) transcriptionally up-regulates erythropoietin, transferrin, and transferrin receptor, leading to increased erythropoiesis and hematopoietic iron supply. To test the hypothesis that ALAS2 expression might be regulated by a similar mechanism, we exposed murine erythroleukemia cells to hypoxia (1% O(2)) and found an up to 3-fold up-regulation of ALAS2 mRNA levels and an increase in cellular heme content. A fragment of the ALAS2 promoter ranging from -716 to +1 conveyed hypoxia responsiveness to a heterologous luciferase reporter gene construct in transiently transfected HeLa cells. In contrast, iron depletion, known to induce HIF-1 activity but inhibit ALAS2 translation, did not increase ALAS2 promoter activity. Mutation of a previously predicted HIF-1-binding site (-323/-318) within this promoter fragment and DNA-binding assays revealed that hypoxic up-regulation is independent of this putative HIF-1 DNA-binding site.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Veterinary Physiology
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2003
Deposited On:11 Feb 2008 12:12
Last Modified:05 Apr 2016 12:12
Publisher:American Society of Hematology
ISSN:0006-4971
Additional Information:This research was originally published in Blood, 2003; 101(1):348-350. Copyright by the American Society of Hematology
Publisher DOI:10.1182/blood-2002-03-0773
Official URL:http://bloodjournal.hematologylibrary.org/cgi/reprint/101/1/348
PubMed ID:12393745
Permanent URL: http://doi.org/10.5167/uzh-48

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