Activation of p53 by MEG3 non-coding RNA
Activation of p53 by MEG3 non-coding RNA
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DOI：
10.1074/jbc.m702029200
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发表时间：
2007-08-24
影响因子：
4.8
通讯作者：
Klibanski, Anne
中科院分区：
文献类型：
--
作者：
Zhou, Yunli;Zhong, Ying;Klibanski, Anne
MEG3是一种母体表达的印迹基因，被认为是一种非编码RNA。我们前期的研究表明MEG3具有抑制肿瘤的功能。肿瘤抑制因子p53在肿瘤抑制中起核心作用，并介导许多其他肿瘤抑制因子的功能。因此，我们假设MEG3通过激活p53发挥作用。我们发现转染MEG3及其同工异构体的表达构建体导致p53蛋白水平显著增加，并显著刺激p53响应启动子的p53依赖性转录。将此作为功能分析，我们证明了MEG3转录物编码的开放阅读框不是MEG3功能所必需的，MEG3 RNA的折叠对其功能至关重要，支持了MEG3作为非编码RNA的概念。我们进一步发现，MEG3通过增强p53与GDF15基因启动子的结合来刺激生长分化因子15 （GDF15）的表达。有趣的是，MEG3不刺激p21（CIP1）的表达，这表明MEG3可以调节p53转录激活的特异性。p53的降解主要由小鼠双分钟2同源物（MDM2）介导。我们发现，在转染MEG3的细胞中，MDM2水平下调，这表明MDM2抑制至少在一定程度上导致了MEG3诱导的p53积累。最后，我们发现MEG3能够在p53缺失的情况下抑制细胞增殖。这些数据表明，MEG3非编码RNA可能具有肿瘤抑制作用，其作用可通过p53依赖性和p53非依赖性途径介导。
MEG3 is a maternally expressed imprinted gene suggested to function as a non-coding RNA. Our previous studies suggest that MEG3 has a function of tumor suppression. The tumor suppressor p53 plays a central role in tumor suppression and mediates the functions of many other tumor suppressors. Therefore, we hypothesized that MEG3 functions through activation of p53. We found that transfection of expression constructs for MEG3 and its isoforms results in a significant increase in p53 protein levels and dramatically stimulates p53-dependent transcription from a p53-responsive promoter. Using this as the functional assay, we demonstrated that the open reading frames encoded by MEG3 transcripts are not required for MEG3 function, and the folding of MEG3 RNA is critical to its function, supporting the concept that MEG3 functions as a non-coding RNA. We further found that MEG3 stimulates expression of the growth differentiation factor 15 (GDF15) by enhancing p53 binding to the GDF15 gene promoter. Interestingly, MEG3 does not stimulate p21(CIP1) expression, suggesting that MEG3 can regulate the specificity of p53 transcriptional activation. p53 degradation is mainly mediated by the mouse double minute 2 homolog (MDM2). We found that MDM2 levels were down-regulated in cells transfected with MEG3, suggesting that MDM2 suppression contributes at least in part to p53 accumulation induced by MEG3. Finally, we found that MEG3 is able to inhibit cell proliferation in the absence of p53. These data suggest that MEG3 non-coding RNA may function as a tumor suppressor, whose action is mediated by both p53-dependent and p53-independent pathways.