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Normoxic destabilization of ATF‐4 depends on proteasomal degradation
Author(s) -
Wottawa M.,
Köditz J.,
Katschinski D. M.
Publication year - 2010
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2009.02060.x
Subject(s) - hypoxia (environmental) , ubiquitin , microbiology and biotechnology , immunoprecipitation , oxygen , transcription factor , chemistry , downregulation and upregulation , proteasome , reactive oxygen species , hypoxia inducible factors , small interfering rna , gene expression , transfection , biology , gene , biochemistry , organic chemistry
Aim: Hypoxia‐inducible gene expression is an important physiological adaptive mechanism in response to a decreased oxygen supply. We have recently described an oxygen‐ and prolyl‐4‐hydroxylase (PHD)3‐dependent stabilization of the activating transcription factor 4 (ATF‐4). The aim of the present study was to examine if the normoxic destabilization of ATF‐4 is regulated by oxygen‐dependent proteasomal degradation. Methods: We determined poly‐ubiquitination of ATF‐4 in normoxia compared to hypoxia by immunoprecipitation and immunoblots. Furthermore, we analysed the expression of the ATF‐4 target gene GADD153 as a function of oxygen concentration. Results: ATF‐4 protein levels were not detectable in normoxia. Normoxic degradation correlated with an oxygen‐dependent poly‐ubiquitination of ATF‐4, which was hindered by hypoxic incubation of the cells. As a result of hypoxia, GADD153 was expressed. The hypoxic GADD153 expression was attenuated or increased by transfecting the cells with ATF‐4 siRNA or PHD3 siRNA respectively. Conclusion: Our results demonstrate the involvement of oxygen‐dependent proteasomal degradation of ATF‐4 in the hypoxia‐induced expression of GADD153. Taken together, hypoxia/PHD3‐regulated stabilization of ATF‐4 by hindering oxygen‐dependent degradation may play a critical role in linking cell fate decisions to oxygen availability.