Dephosphorylated hypoxia-inducible factor 1alpha as a mediator of p53-dependent apoptosis during hypoxia.

Under hypoxia, HIF-1alpha binds to aryl hydrocarbon receptor nuclear translocator (ARNT, also called HIF-1beta) to activate expression of genes important for cell survival. Alternatively, HIF-1alpha can bind to the tumor suppressor p53 and promote p53-dependent apoptosis. Here we show that the opposite functions of HIF-1alpha are distinguished by its phosphorylation ...
status. Two distinguishable forms of HIF-1alpha, phosphorylated and dephosphorylated, were induced during hypoxia-induced apoptosis. The phosphorylated HIF-1alpha was the major form that bound to ARNT. Ectopically expressed ARNT was consistently able to enhance HIF-1alpha phosphorylation in a binding-dependent manner. In contrast, the dephosphorylated HIF-1alpha was the major form that bound to p53. Depletion of the dephosphorylated HIF-1alpha, by using the Hsp90 inhibitor geldanamycin A that had little effect on the phosphorylated HIF-1alpha expression, suppressed p53 induction and subsequent apoptosis. Depletion of dephosphorylated HIF-1alpha also prevented hypoxia-induced nuclear accumulation of HDM2, a negative regulator of p53. Our results indicate that the functions of HIF-1alpha varied with its phosphorylation status and that dephosphorylated HIF-1alpha mediated apoptosis by binding to and stabilizing p53.
Mesh Terms:
Apoptosis, Aryl Hydrocarbon Receptor Nuclear Translocator, Benzoquinones, Caspases, Cell Hypoxia, Cell Nucleus, DNA-Binding Proteins, HSP90 Heat-Shock Proteins, Humans, Hypoxia-Inducible Factor 1, Hypoxia-Inducible Factor 1, alpha Subunit, Lactams, Macrocyclic, Nuclear Proteins, Phosphorylation, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-mdm2, Quinones, Receptors, Aryl Hydrocarbon, Transcription Factors, Tumor Suppressor Protein p53
Oncogene
Date: Sep. 13, 2001
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