Effect of mutations on the p53 IRES RNA structure Implications for de-regulation of the synthesis of p53 isoforms
Effect of mutations on the p53 IRES RNA structure Implications for de-regulation of the synthesis of p53 isoforms
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DOI：
10.4161/rna.8.1.14260
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发表时间：
2011-01-01
期刊：
影响因子：
4.1
通讯作者：
Das, Saumitra
中科院分区：
文献类型：
--
作者：
Grover, Richa;Sharathchandra, Arandkar;Das, Saumitra
早期，我们已经证明了肿瘤抑制基因p53 mRNA内存在内部核糖体进入位点（IRES）。在这里，我们绘制了推定的二级结构的p53-IRES RNA使用化学探测和核酸酶作图实验的信息。此外，将野生型RNA的IRES元件的二级结构与癌症来源的沉默突变体p53 RNA进行比较。这些突变可能导致p53-IRES RNA的构象改变。结果还表明，与野生型RNA相比，突变体的IRES活性降低。此外，观察到对于增强IRES功能至关重要的一些细胞质反式作用因子不能像野生型那样有效地结合突变体RNA。我们的研究结果表明，hnRNP C1/C2结合p53-IRES和siRNA介导的hnRNP C1/C2的部分沉默显示IRES功能明显下降，相应的p53亚型的水平随之下降。有趣的是，突变型p53 IRES与hnRNP C1/C2蛋白的结合较少。最后，在阿霉素治疗后，突变体RNA无法显示与野生型相比类似程度的p53合成增强。总之，这些观察结果表明，突变发生在p53 IRES可能有深刻的影响，其表达和活性的失调。
Earlier we have demonstrated the presence of internal ribosome entry site (IRES) within tumor suppressor p53 mRNA. Here we have mapped the putative secondary structure of p53-IRES RNA using information from chemical probing and nuclease mapping experiments. Additionally, the secondary structure of the IRES element of the wild-type RNA was compared with cancer-derived silent mutant p53 RNAs. These mutations might result in the conformational alterations of p53-IRES RNAs. The results also indicate decreased IRES activities of the mutants as compared to wild-type RNA. Further, it was observed that some of the cytoplasmic trans-acting factors, critical for enhancing IRES function, were unable to bind mutant RNAs as efficiently as to wild-type. Our results suggest that hnRNP C1/C2 binds to p53-IRES and siRNA mediated partial silencing of hnRNP C1/C2 showed appreciable decrease in IRES function and consequent decrease in the level of the corresponding p53 isoform. Interestingly mutant p53 IRES showed lesser binding with hnRNP C1/C2 protein. Finally, upon doxorubicin treatment, the mutant RNAs were unable to show enhanced p53 synthesis to similar extent compared to wild type. Taken together, these observations suggest that mutations occurring in the p53 IRES might have profound implications for de-regulation of its expression and activity.