Department of Pediatrics, University of Illinois at Chicago, Chicago, Illinois, United States.
Department of Medical Genetics, Second Military Medical University, Shanghai, People's Republic of China.
Am J Physiol Lung Cell Mol Physiol. 2024 Jul 1;327(1):L102-L113. doi: 10.1152/ajplung.00127.2023. Epub 2024 Mar 19.
We have reported previously that during hypoxia exposure, the expression of mature miR-17∼92 was first upregulated and then downregulated in pulmonary artery smooth muscle cells (PASMC) and in mouse lungs in vitro and in vivo. Here, we investigated the mechanisms regulating this biphasic expression of miR-17∼92 in PASMC in hypoxia. We measured the level of primary miR-17∼92 in PASMC during hypoxia exposure and found that short-term hypoxia exposure (3% O, 6 h) induced the level of primary miR-17∼92, whereas long-term hypoxia exposure (3% O, 24 h) decreased its level, suggesting a biphasic regulation of miR-17∼92 expression at the transcriptional level. We found that short-term hypoxia-induced upregulation of miR-17∼92 was hypoxia-inducible factor 1α (HIF1α) and E2F1 dependent. Two HIF1α binding sites on miR-17∼92 promoter were identified. We also found that long-term hypoxia-induced suppression of miR-17∼92 expression could be restored by silencing of p53. Mutation of the p53-binding sites in the miR-17∼92 promoter increased miR-17∼92 promoter activity in both normoxia and hypoxia. Our findings suggest that the biphasic transcriptional regulation of miR-17∼92 during hypoxia is controlled by HIF1/E2F1 and p53 in PASMC: during short-term hypoxia exposure, stabilization of HIF1 and induction of E2F1 induce the transcription of miR-17∼92, whereas during long-term hypoxia exposure, hyperphosphorylation of p53 suppresses the expression of miR-17∼92. We showed that the biphasic transcriptional regulation of miR-17∼92 during hypoxia is controlled by two distinct mechanisms: during short-term hypoxia exposure, induction of HIF1 and E2F1 upregulates miR-17∼92. Longer hypoxia exposure induces hyperphosphorylation of p53 at ser15, which leads to its binding to miR-17∼92 promoter and inhibition of its expression. Our findings provide novel insights into the spatiotemporal regulation of miR-17∼92 that may play a role in the development of human lung diseases including pulmonary hypertension (PH).
我们之前曾报道，在低氧暴露期间，肺动脉平滑肌细胞（PASMC）和体内外的小鼠肺中，成熟的 miR-17∼92 的表达首先上调，然后下调。在这里，我们研究了调节低氧诱导的 PASMC 中 miR-17∼92 这种双相表达的机制。我们在低氧暴露期间测量了 PASMC 中初级 miR-17∼92 的水平，发现短期低氧暴露（3% O，6 h）诱导初级 miR-17∼92 的水平，而长期低氧暴露（3% O，24 h）则降低其水平，提示 miR-17∼92 表达在转录水平上呈双相调节。我们发现，短期低氧诱导的 miR-17∼92 上调依赖于缺氧诱导因子 1α（HIF1α）和 E2F1。miR-17∼92 启动子上鉴定出两个 HIF1α 结合位点。我们还发现，通过沉默 p53 可以恢复长期低氧诱导的 miR-17∼92 表达抑制。miR-17∼92 启动子中 p53 结合位点的突变增加了正常氧和低氧条件下 miR-17∼92 启动子的活性。我们的研究结果表明，HIF1/E2F1 和 p53 在 PASMC 中控制了 miR-17∼92 在低氧时的双相转录调节：在短期低氧暴露期间，HIF1 的稳定和 E2F1 的诱导诱导 miR-17∼92 的转录，而在长期低氧暴露期间，p53 的过度磷酸化抑制 miR-17∼92 的表达。我们表明，miR-17∼92 在低氧时的双相转录调节受两种不同机制控制：在短期低氧暴露期间，诱导 HIF1 和 E2F1 上调 miR-17∼92。更长时间的低氧暴露诱导 p53 在丝氨酸 15 处过度磷酸化，导致其与 miR-17∼92 启动子结合并抑制其表达。我们的研究结果为 miR-17∼92 的时空调节提供了新的见解，这可能在包括肺动脉高压（PH）在内的人类肺部疾病的发展中发挥作用。
