Characterization of the activation of protein tyrosine phosphatase, receptor-type, Z polypeptide 1 (PTPRZ1) by hypoxia inducible factor-2 alpha.
BACKGROUND
Hypoxia inducible factors (HIFs) are the principal means by which cells upregulate genes in response to hypoxia and certain other stresses. There are two major HIFs, HIF-1 and HIF-2. We previously found that certain genes are preferentially activated by HIF-2. One was protein tyrosine phosphatase, receptor-type, Z polypeptide 1 (PTPRZ1). PTPRZ1 is overexpressed in a number of tumors and has been implicated in glioblastoma pathogenesis.


RESULTS
To understand the preferential activation of PTPRZ1 by HIF-2, we studied the PTPRZ1 promoter in HEK293T cells and Hep3B cells. Through deletion and mutational analysis, we identified the principal hypoxia response element. This element bound to both HIF-1 and HIF-2. We further identified a role for ELK1, an E26 transformation-specific (Ets) factor that can bind to HIF-2alpha but not HIF-1alpha, in the HIF-2 responsiveness. Knock-down experiments using siRNA to ELK1 decreased HIF-2 activation by over 50%. Also, a deletion mutation of one of the two Ets binding motifs located near the principal hypoxia response element similarly decreased activation of the PTPRZ1 promoter by HIF-2. Finally, chromatin immunoprecipitation assays showed binding of HIF and ELK1 to the PTPRZ1 promoter region.


CONCLUSIONS
These results identify HIF-binding and Ets-binding motifs on the PTPRZ1 promoter and provide evidence that preferential activation of PTPRZ1 by HIF-2 results at least in part from cooperative binding of HIF-2 and ELK1 to nearby sites on the PTPRZ1 promoter region. These results may have implications in tumor pathogenesis and in understanding neurobiology, and may help inform the development of novel tumor therapy.
HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
Victoria
V
Wang
David A
DA
Davis
Ravindra P
RP
Veeranna
Muzammel
M
Haque
Robert
R
Yarchoan
D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002460:Cell Line; D004252:DNA Mutational Analysis; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5 / Q000378:metabolism*; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D034741:RNA, Small Interfering; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5; D050807:ets-Domain Protein Elk-1; D000099162:Endothelial PAS Domain-Containing Protein 1; C494112:ELK1 protein, human; C497442:HIF1A protein, human; C516895:PTPRZ1 protein, human