A novel mode of action of YC-1 in HIF inhibition: stimulation of FIH-dependent p300 dissociation from HIF-1{alpha}.
Hypoxia-inducible factor (HIF)-1 plays a key role in tumor promotion by inducing approximately 60 genes required for tumor adaptation to hypoxia; thus, it is viewed as a target for cancer therapy. For this reason, YC-1, which down-regulates HIF-1alpha and HIF-2alpha at the post-translational level, is being developed as a novel ... anticancer drug. We here found that YC-1 acts in a novel manner to inhibit HIF-1. In the Gal4 reporter system, which is not degraded by YC-1, YC-1 was found to significantly inactivate the COOH-terminal transactivation domain (CAD) of HIF-1alpha, whereas it failed to inactivate CAD(N803A) mutant. In coimmunoprecipitation assays, YC-1 stimulated factor inhibiting HIF (FIH) binding to CAD even in hypoxia, whereas it failed to increase the cellular levels of hydroxylated Asn803 of CAD. It was also found that YC-1 prevented p300 recruitment by CAD in mammalian two-hybrid and coimmunoprecipitation assays. The involvement of FIH in YC-1-induced CAD inactivation was confirmed in EPO-enhancer and Gal4 reporter systems using FIH small interfering RNA and dimethyloxalylglycine FIH inhibitor. Indeed, FIH inhibition rescued HIF target gene expressions repressed by YC-1. In cancer cell lines other than Hep3B, YC-1 inhibits HIF-1alpha via the FIH-dependent CAD inactivation as well as via the protein down-regulation. Given these results, we suggest that the functional inactivation of HIF-alpha contributes to the YC-1-induced deregulation of hypoxia-induced genes.
Mesh Terms:
Amino Acids, Dicarboxylic, Cell Line, Tumor, Enzyme Activators, Gene Expression Regulation, Neoplastic, Genes, Reporter, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Indazoles, Mixed Function Oxygenases, Models, Biological, Plasmids, Protein Biosynthesis, RNA, Small Interfering, Repressor Proteins, Transcriptional Activation, p300-CBP Transcription Factors
Amino Acids, Dicarboxylic, Cell Line, Tumor, Enzyme Activators, Gene Expression Regulation, Neoplastic, Genes, Reporter, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Indazoles, Mixed Function Oxygenases, Models, Biological, Plasmids, Protein Biosynthesis, RNA, Small Interfering, Repressor Proteins, Transcriptional Activation, p300-CBP Transcription Factors
Mol. Cancer Ther.
Date: Dec. 01, 2008
PubMed ID: 19074848
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