DNA damage is a prerequisite for p53-mediated proteasomal degradation of HIF-1alpha in hypoxic cells and downregulation of the hypoxia marker carbonic anhydrase IX.
We investigated the relationship between the tumor suppressor p53 and the hypoxia-inducible factor-1 (HIF-1)-dependent expression of the hypoxia marker, carbonic anhydrase IX (CAIX). MCF-7 (wt p53) and Saos-2 (p53-null) cells displayed similar induction of CAIX expression and CA9 promoter activity under hypoxic conditions. Activation of p53 by the DNA damaging agent mitomycin C (MC) was accompanied by a potent repression of CAIX expression and the CA9 promoter in MCF-7 but not in Saos-2 cells. The activated p53 mediated increased proteasomal degradation of HIF-1alpha protein, resulting in considerably lower steady-state levels of HIF-1alpha protein in hypoxic MCF-7 cells but not in Saos-2 cells. Overexpression of HIF-1alpha relieved the MC-induced repression in MCF-7 cells, confirming regulation at the HIF-1alpha level. Similarly, CA9 promoter activity was downregulated by MC in HCT 116 p53(+/+) but not the isogenic p53(-/-) cells. Activated p53 decreased HIF-1alpha protein levels by accelerated proteasome-dependent degradation without affecting significantly HIF-1alpha transcription. In summary, our results demonstrate that the presence of wtp53 under hypoxic conditions has an insignificant effect on the stabilization of HIF-1alpha protein and HIF-1-dependent expression of CAIX. However, upon activation by DNA damage, wt p53 mediates an accelerated degradation of HIF-1alpha protein, resulting in reduced activation of CA9 transcription and, correspondingly, decreased levels of CAIX protein. A model outlining the quantitative relationship between p53, HIF-1alpha, and CAIX is presented.
Kaluzová
Milota
M
Department of Microbiology and Molecular Genetics, University of California at Irvine, College of Medicine, Irvine 92717, USA.
Kaluz
Stefan
S
Lerman
Michael I
MI
Stanbridge
Eric J
EJ
D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004249:DNA Damage; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000201:enzymology / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016685:Mitomycin / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
D000951:Antigens, Neoplasm; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; D003546:Cysteine Endopeptidases; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases