Up-regulation of apoptosis inhibitory protein IAP-2 by hypoxia. Hif-1-independent mechanisms.
Hypoxia is a key determinant of tissue pathology during tumor development and organ ischemia. However, little is known regarding hypoxic regulation of genes that are directly involved in cell death or death resistance. Here we report the striking induction by severe hypoxia of the anti-apoptotic protein IAP-2. Hypoxic cells with IAP-2 up-regulation became resistant to apoptosis. IAP-2 was induced by hypoxia per se rather than by the secondary effects of hypoxia, including ATP depletion and cell injury. The inductive response did not relate to alterations of cellular redox status or arrest of mitochondrial respiration. On the other hand, IAP-2 induction was attenuated by actinomycin D, suggesting a role for gene transcription. In vitro nuclear run-on assays demonstrated specific increases in IAP-2 transcriptional activity after hypoxia exposure. HIF-1, the primary transcription factor that is responsible for multiple gene activation under hypoxia, does not have a role in IAP-2 expression. HIF-1 and IAP-2 were induced by different degrees of hypoxia; severe hypoxia or anoxia was required for IAP-2 induction. Moreover, cobalt chloride and desferrioxamine activated HIF-1 but not IAP-2. Finally, IAP-2 was induced by severe hypoxia in mouse embryonic stem cells that were deficient of HIF-1. Thus, this study not only provides the first demonstration of hypoxic regulation of an anti-apoptotic gene but also suggests the participation of novel hypoxia-responsive transcription mechanisms.
Department of Pathology, University of Texas Health Science Center, San Antonio, Texas 78229, USA. dong@uthscsa.edu
Z
Z
Dong
M A
MA
Venkatachalam
J
J
Wang
Y
Y
Patel
P
P
Saikumar
G L
GL
Semenza
T
T
Force
J
J
Nishiyama
D016475:3T3 Cells; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D016587:Antimutagenic Agents / Q000494:pharmacology; D017209:Apoptosis; D015152:Blotting, Northern; D002460:Cell Line; D002467:Cell Nucleus; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D006801:Humans; D000860:Hypoxia; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015151:Immunoblotting; D051034:Inhibitor of Apoptosis Proteins; D007668:Kidney / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D013234:Stem Cells; D014157:Transcription Factors; D014158:Transcription, Genetic; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D016587:Antimutagenic Agents; D002614:Chelating Agents; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D051034:Inhibitor of Apoptosis Proteins; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D014157:Transcription Factors; D003609:Dactinomycin; D003035:Cobalt; D000255:Adenosine Triphosphate; C018021:cobaltous chloride; D003676:Deferoxamine; D010100:Oxygen