Negative regulation of hypoxia inducible factor-1alpha by necdin.

Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor that mediates cellular and systemic homeostatic responses to reduce O2 availability, such as erythropoiesis, angiogenesis, and glycolysis. Using the yeast two-hybrid screening system, we found that the oxygen dependent degradation (ODD) domain of HIF-1alpha interacts with necdin, a growth suppressor. The interaction of necdin with HIF-1alpha was confirmed using coimmunoprecipitation with the overexpressed HIF-1alpha. Biological effect of necdin on HIF-1alpha showed that necdin reduces the transcriptional activity of HIF-1 under hypoxia. Moreover, necdin decreased the level of the HIF-1alpha protein, but not that of mRNA, implying a possibility of necdin-mediated HIF-1alpha degradation. Furthermore, necdin has an anti-angiogenic activity in the tube formation assay and CAM assay, which might be due to the downregulation of HIF-1alpha. Collectively, these results suggest that necdin can be a novel negative regulator of HIF-1alpha stability via the direct interaction.