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Hydroxylation of Hypoxia-Inducible Transcription Factors and Chemical Compounds Targeting the HIF-α Hydroxylases

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Abstract:

The hypoxia-inducible transcription factors (HIFs) are central components in the cellular responses to a lack of O2, i.e. hypoxia. Homologs of the HIF system (HIF-1, -2 and -3) are detectable in all nucleated cells of multicellular organisms. Active HIFs are heterodimers (HIF-α/β). In hypoxia the O2-labile α-subunit is translocated to the nucleus where it binds HIF-β. Over 100 HIF target genes have already been identified. The translational products of these genes increase O2 delivery to hypoxic tissues, such as erythropoietin which stimulates the production of red blood cells, and they adapt cellular metabolism to hypoxia, such as glycolytic enzymes. HIFs are inactive in normoxia because of O2-dependent enzymatic hydroxylation and subsequent degradation of their α-subunit. Three HIF-α prolyl hydroxylases (PHD1, 2 and 3) initiate proteasomal degradation while an asparaginyl hydroxylase (factor inhibiting HIF-1, FIH-1) inhibits the function of the C-terminal transactivation domain of HIF-α. In addition to O2 and 2-oxoglutarate, the HIF-α hydroxylases require Fe2+ and ascorbate as co-factors. Products of glycolysis can act as endogenous inhibitors of HIF hydroxylases which may lead to sustained activation of HIFs in cancer cells. The cofactor requirements define the routes to inhibition of the enzymes when HIF activation is desirable. In particular, 2- oxoglutarate analogues have emerged as promising tools for stimulation of erythropoiesis and angiogenesis (“HIF-stabilizers”). However, as the HIF system promotes the transcription of many genes, and other 2-oxoglutarate dependent dioxygenases are likely to be inhibited by the same analogues, careful evaluation of the inhibitors seems mandatory prior to their clinical use.

Keywords: Hypoxia; dioxygenase; gene expression; hydroxylation; oxygen; transcription factor

Document Type: Research Article

DOI: http://dx.doi.org/10.2174/092986707781058850

Affiliations: Institute for Physiology, University of Luebeck, D-23538 Luebeck, Germany.

Publication date: July 1, 2007

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  • Current Medicinal Chemistry covers all the latest and outstanding developments in medicinal chemistry and rational drug design. Each issue contains a series of timely in-depth reviews written by leaders in the field covering a range of the current topics in medicinal chemistry. Current Medicinal Chemistry is an essential journal for every medicinal chemist who wishes to be kept informed and up-to-date with the latest and most important developments.
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