title: Activating transcription factor 2 increases transactivation and protein stability of hypoxia-inducible factor 1alpha in hepatocytes.
abstract: HIF-1 (hypoxia inducible factor 1) performs a crucial role in mediating the response to hypoxia. However, other transcription factors are also capable of regulating hypoxia-induced target-gene transcription. In a previous report, we demonstrated that the transcription factor ATF-2 (activating transcription factor 2) regulates hypoxia-induced gene transcription, along with HIF-1alpha. In the present study, we show that the protein stability of ATF-2 is induced by hypoxia and the hypoxia-mimic CoCl2 (cobalt chloride), and that ATF-2 induction enhances HIF-1alpha protein stability via direct protein interaction. The knockdown of ATF-2 using small interfering RNA and translation-inhibition experiments demonstrated that ATF-2 plays a key role in the maintenance of the expression level and transcriptional activity of HIF-1alpha. Furthermore, we determined that ATF-2 interacts directly with HIF-1alpha both in vivo and in vitro and competes with the tumour suppressor protein p53 for HIF-1alpha binding. Collectively, these results show that protein stabilization of ATF-2 under hypoxic conditions is required for the induction of the protein stability and transactivation activity of HIF-1alpha for efficient hypoxia-associated gene expression.
authors.affiliation: Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: Jeong Hae
authors.initials: JH
authors.lastname: Choi
authors.forename: Hyun Kook
authors.initials: HK
authors.lastname: Cho
authors.forename: Yung Hyun
authors.initials: YH
authors.lastname: Choi
authors.forename: JaeHun
authors.initials: J
authors.lastname: Cheong
mesh_terms: D051698:Activating Transcription Factor 2 / Q000378:metabolism*; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D003035:Cobalt / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D055550:Protein Stability; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016159:Tumor Suppressor Protein p53; D003035:Cobalt; C018021:cobaltous chloride