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CHARACTERIZATION OF ENDOGENOUS HYPDXIA-INDUCED TRANSCRIPTIONAL REPRESSOR HIF-3ALPHA

内源性缺氧诱导的转录抑制子 HIF-3ALPHA 的表征

基本信息

批准号：
18590071
负责人：
HARA Shuntaro
金额：
$ 2.55万
依托单位：
Showa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

Hypoxia-inducible factor (HIF) is an important transcriptional factor that is activated when mammalian cells experience hypoxia, a tumor microenvironmental condition that plays a pivotal role in tumor progression and treatment. HIF consists of oxygen-sensitive HIF-α and constitutively expressed HIF-β subunits. The recently identified third member of the human HIF-α, HIF-3α, produces multiple splicing variants. Here we cloned cDNA for one of the splicing variants of human HIF-3α, HIF-3α2, from human kidney and examined its characteristics. HIF-3α2, as well as the first identified HIF-3α variant HIF-3α1, localized in the nucleus and was stabilized under hypoxia when ectopically expressed in COS-7 cells. However, reporter gene analysis showed that HIF-3α2 failed to activate HIF-mediated transcription and conversely suppressed it, although HIF-3a1 with an N-terminal domain identical to HIF-3α2 had the ability to activate it. C-terminal deletion analysis revealed that the C-terminal moiety of HIF-3α2 masked its own transcriptional activity. We further showed that overexpression of HIF-3α2 in renal carcinoma VMRC inhibited both hypoxia-inducible gene expression in vitro and growth as xenografts in vivo. These results indicated that HIF-3α2, which is stabilized under hypoxia, functions as a negative regulator of hypoxia-inducible gene expression in a novel feedback mechanism.

缺氧诱导因子（HIF）是一种重要的转录因子，当哺乳动物细胞经历缺氧时被激活，缺氧是一种在肿瘤进展和治疗中起关键作用的肿瘤微环境条件。HIF由氧敏感性HIF-α和组成性表达的HIF-β亚基组成。最近发现的人HIF-α的第三个成员，HIF-3α，产生多种剪接变体。我们从人肾脏中克隆了人HIF-3α剪接变体之一HIF-3α2的cDNA，并对其特性进行了研究。HIF-3α2以及第一个鉴定的HIF-3α变体HIF-3α1定位于细胞核，并在COS-7细胞中异位表达时在缺氧条件下稳定。报告基因分析表明，HIF-3α2不能激活HIF介导的转录，相反，HIF-3α2抑制HIF介导的转录，而HIF-3a 1具有激活HIF-3α2的能力，C端缺失分析表明HIF-3α2的C端部分掩盖了其自身的转录活性。我们进一步发现，HIF-3α2在肾癌VMRC中的过表达抑制了体外缺氧诱导基因表达和体内异种移植生长。这些结果表明，HIF-3α2在低氧条件下稳定，在一种新的反馈机制中作为低氧诱导基因表达的负调节剂发挥作用。