Analysis of the inhibitory mechanisms of IFN gamma induced gene expression by hypoxia

我们先前已经表明，缺氧下调IFN诱导的人肿瘤细胞系中趋化因子CXCL 9和CXCL 10基因的表达。 我们探讨了低氧下调IFN诱导的基因表达的机制，发现虽然HIF-1不参与IFN诱导的基因的转录抑制，但低氧抑制了辅激活因子SRC-1 Pol II的募集。 在这项研究中，我们研究了HIF-2，组蛋白甲基化在CXCL 9基因的启动子区域，和介质复合物，参与招募的Pol II缺氧介导的转录抑制的潜在参与。 在HEK 293细胞中过表达活性形式的HIF-2抑制CXCL 9启动子活性，表明HIF-2负调节CXCL 9表达。实时定量RT-PCR分析表明，HSC-2细胞中观察到甲基转移酶和介体复合物成员的mRNA的组成性表达。

We have previously shown that hypoxia down-regulated the IFN-induced expression of chemokine CXCL9 and CXCL10 genes in human tumor cell lines. We have explored the mechanisms by which hypoxia down-regulates the IFN-induced gene expressions and found that although HIF-1 was not involved in the transcriptional repression of the IFN-induced genes, recruitments of Pol II, coactivator SRC-1 were inhibited under the hypoxia. In this study, we investigated potential involvements of HIF-2, histone methylation at the promoter region of the CXCL9 genes, and mediator complex that participates in the recruitment of Pol II for the hypoxia-mediated transcriptional repression. Over expression of an active form of HIF-2 in HEK293 cells inhibited the CXCL9 promoter activity, suggesting that HIF-2 negatively regulates CXCL9 expression. Real-time RT-PCR analysis showed that constitutive expressions of mRNAs for methyltransferase and members of mediator complex were observed in HSC-2 cells.