Department of Immunology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
J Immunol. 2010 Feb 1;184(3):1484-91. doi: 10.4049/jimmunol.0902423. Epub 2009 Dec 30.
IL-17 contributes to inflammatory response in part by promoting enhanced expression of chemokines, such as CXCL1, by prolonging the t(1/2) of this constitutively unstable mRNA. Although IL-17 is a weak stimulus for transcription of the CXCL1 gene, it strongly potentiates message accumulation via stabilization when the mRNA is transcribed in cells stimulated with TNF. In myeloid cells, LPS-induced CXCL1 mRNA stabilization is dependent on AUUUA-containing sequence motifs that are recognized by the RNA binding protein tristetraprolin (TTP). Using deletion and site-specific mutagenesis, we report that IL-17-mediated stabilization of CXCL1 mRNA in nonmyeloid cells depends on a sequence that does not contain the AUUUA motif. Furthermore, a specific two-nucleotide mutation within this region markedly abrogates sensitivity for IL-17-mediated stabilization. Consistent with this finding, the IL-17-sensitive sequence does not exhibit increased instability in the presence of TTP, and CXCL1 mRNA remains unstable and can be stabilized in response to treatment with IL-17 in embryo fibroblasts from mice in which the TTP gene has been deleted. Whereas the RNA binding protein KSRP has been shown to participate in regulating the instability of human CXCL8 mRNA, inhibitory RNA-based reduction in KSRP does not effect the instability mediated by the IL-17-sensitive sequence motif. These findings suggest that IL-17-mediated chemokine mRNA stabilization in nonmyeloid cells uses a mechanism that is distinct from that operating to control AU-rich mRNA stability in myeloid cells.
IL-17 通过促进趋化因子（如 CXCL1）的表达，从而在部分程度上促进炎症反应，其方法是延长这种固有不稳定 mRNA 的 t(1/2)。虽然 IL-17 是刺激 CXCL1 基因转录的弱刺激物，但当 TNF 刺激的细胞中转录该 mRNA 时，它通过稳定作用强烈增强消息积累。在髓样细胞中，LPS 诱导的 CXCL1 mRNA 稳定依赖于 AUUUA 富含序列基序，该基序被 RNA 结合蛋白 tristetraprolin (TTP) 识别。通过缺失和定点诱变，我们报告在非髓样细胞中，IL-17 介导的 CXCL1 mRNA 稳定依赖于不包含 AUUUA 基序的序列。此外，该区域内的特定两个核苷酸突变显著消除了对 IL-17 介导的稳定作用的敏感性。与这一发现一致的是，在 TTP 存在的情况下，IL-17 敏感序列不会表现出增加的不稳定性，并且 CXCL1 mRNA 仍然不稳定，并且可以响应 IL-17 的治疗而稳定在 TTP 基因已被删除的小鼠的胚胎成纤维细胞中。尽管 RNA 结合蛋白 KSRP 已被证明参与调节人 CXCL8 mRNA 的不稳定性，但基于抑制性 RNA 的 KSRP 减少不会影响 IL-17 敏感序列基序介导的不稳定性。这些发现表明，IL-17 在非髓样细胞中调节趋化因子 mRNA 稳定性的机制与控制髓样细胞中富含 AU 的 mRNA 稳定性的机制不同。
