Yang Bin, Hu Peishan, Lin Xihua, Han Wei, Zhu Liyuan, Tan Xiaochao, Ye Fei, Wang Guanzhou, Wu Fan, Yin Bin, Bao Zhaoshi, Jiang Tao, Yuan Jiangang, Qiang Boqin, Peng Xiaozhong
The State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, 100005, People's Republic of China.
The State Key Laboratory of Cardiovascular Disease, Fuwai Hospital and National Center of Cardiovascular Disease, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 102300, People's Republic of China.
Cell Mol Life Sci. 2015 Nov;72(22):4383-97. doi: 10.1007/s00018-015-1938-7. Epub 2015 Jun 6.
Internal ribosomal entry site (IRES)-mediated translation initiation is constitutively activated during stress conditions such as tumorigenesis and hypoxia. The RNA editing enzyme ADAR1 plays an important role in physiology and pathology. Initially, we found that the ADAR1 p150 or p110 transcript levels were decreased in glioma cells compared with normal astrocyte cells. In contrast, protein levels of ADAR1 p110 were significantly upregulated in glioma tissues and cells. This expression pattern indicated translationally controlled regulation. We identified an 885-nt sequence that was located between AUG1 and AUG2 within the ADAR1 mRNA that exhibited IRES-like activity. Furthermore, we confirmed that the translational mode of ADAR1 p110 was mediated by PTBP1 in glioma cells. The protein levels of PTBP1 and ADAR1 were cooperatively expressed in glioma tissues and cells. Knocking down ADAR1 p110 significantly decreased cell proliferation in three types of glioma cells (T98G, U87MG and A172). The removal of a minimal IRES-like sequence in a p150-overexpression construct could effectively abolish p110 induction and resulted in the slight suppression of cell proliferation compared with ADAR1-p150 overexpression in siPTBP1-treated T98G cells. In summary, our study revealed a mechanism whereby ADAR1 p110 can be activated by PTBP1 through an IRES-like element in glioma cells, and ADAR1 is essential for the maintenance of gliomagenesis.
内部核糖体进入位点（IRES）介导的翻译起始在诸如肿瘤发生和缺氧等应激条件下被持续激活。RNA编辑酶ADAR1在生理和病理过程中发挥重要作用。最初，我们发现与正常星形胶质细胞相比，胶质瘤细胞中ADAR1 p150或p110的转录水平降低。相反，ADAR1 p110的蛋白水平在胶质瘤组织和细胞中显著上调。这种表达模式表明存在翻译水平的调控。我们在ADAR1 mRNA的AUG1和AUG2之间鉴定出一个885 nt的序列，该序列具有类似IRES的活性。此外，我们证实胶质瘤细胞中ADAR1 p110的翻译模式由PTBP1介导。PTBP1和ADAR1的蛋白水平在胶质瘤组织和细胞中协同表达。敲低ADAR1 p110显著降低了三种胶质瘤细胞（T98G、U87MG和A172）的细胞增殖。在siPTBP1处理的T98G细胞中，与ADAR1-p150过表达相比，p150过表达构建体中最小类似IRES序列的缺失可有效消除p110的诱导并导致细胞增殖的轻微抑制。总之，我们的研究揭示了一种机制，即ADAR1 p110在胶质瘤细胞中可通过类似IRES的元件被PTBP1激活，并且ADAR1对于维持胶质瘤发生至关重要。
