Identification and clinical application of a novel regulatory proteins under hypoxic stress

低氧诱导因子-1α是一种转录因子，控制低氧压反应基因的表达，包括血管内皮生长因子、红细胞生成素和糖酵解酶。HIF-1a的激活是通过与转录共激活因子cAMP反应元件结合蛋白结合蛋白(CBP)/p300结合来调节的。利用酵母双杂交筛选系统，我们发现HIF-1α的抑制区与组蛋白脱乙酰基酶7的C-末端结构域有很强的相互作用。邻硝基苯基β-D-半乳糖苷分析表明，HIF-1α的第735-785位氨基酸和HDAC7的669-952位氨基酸是相互作用的最小接触部位。在常氧和低氧(2%，O2)条件下生长的HEK293细胞中，HDAC7与HIF-1α的结合重现。在其他HIF-α家族成员中，HDAC7只与HIF-1α结合，包括HIF-2α和HIF-3α，而HIF-1α只与HDAC家族中的HDAC7相互作用。尽管在正常氧浓度下，HDAC7主要定位于细胞质中，但在细胞核中，HDAC7通过与HIF-1α、HDAC7和p300形成复合体，增加了HIF-1α的转录活性。这些结果表明，HDAC7是一种新的HIF-1α转录激活剂。目前我们发现，从低氧状态向常氧状态(复氧)转变时，HDAC7从HDAC7/HIF-1α复合体中分离出来并输出到细胞质中，调节了HIF-1α的降解。

Hypoxia-inducible factor (HIF)-1α is a transcription factor that controls expression of genes responsive to low oxygen tension, including vascular endothelial growth factor, erythropoien, and glycolytic enzymes. The activation of HIF-1a is regulated by binding to the transcriptional co-activator cAMP response element-binding protein-binding protein (CBP)/p300. Using the yeast two-hybrid screening system, we found that the inhibitory domain of HIF-1α strongly interacted with the C-terminal domain of histone deacetylase (HDAC)7. The o-nitrophenyl β-D-galactopyranoside assay revealed that regions containing amino acids 735-785 of HIF-1α and amino acids 669-952 of HDAC7 were minimum contact sites of the interaction. The binding of HDAC7 with HIF-1α was reproduced in HEK293 cells grown under normoxic and hypoxic condition (2%, O2). HDAC7 bound solely to HIF-1α among other HIF-α family members, including HIF-2α and HIF-3α, whereas HIF-1α only interacted with HDAC7 in the class HDAC family. Although HDAC7 was localized dominantly in the cytoplasm at normal oxygen concentrations, In the nucleus, HDAC7 increased transcriptional activity of HIF-1α through the formation of a complex with HIF-1α, HDAC7 and p300. Token together, these results indicated that HDAC7 is a novel transcriptional activator of HIF-1α. Currently we found that disscociation of HDAC7 from HDAC7/HIF-1α complex and the export of HDAC7 to the cytoplasm regulated HIF-1α degradation upon the transition from hypoxic oxygen condition to normal oxygen condition (re-oxygenation).