Epstein-Barr virus U leader exon contains an internal ribosome entry site
Epstein-Barr virus U leader exon contains an internal ribosome entry site
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DOI：
10.1038/sj.onc.1206149
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发表时间：
2003-01-30
期刊：
影响因子：
8
通讯作者：
Ricksten, A
中科院分区：
文献类型：
--
作者：
Isaksson, Å;Berggren, M;Ricksten, A
真核生物的翻译可以通过帽依赖机制或通过内部核糖体进入来启动，在这个过程中，核糖体被直接招募到起始密码子上游的信使核糖核酸结构区域。在这里，我们报告了在Epstein-Barr核抗原1(EBNA1)基因的非翻译区发现了一个内部核糖体进入位点(IRES)。EBNA1是在EB病毒潜伏期和病毒裂解周期的所有已知状态中唯一表达的核蛋白，是维持EBV Episome所必需的。通过构建报告基因和体外转染实验，我们发现在不同的Burkitt淋巴瘤细胞系中，FP和QP启动的EBNA1基因5‘非翻译区的序列使EBNA1的表达水平增加4-14倍。双顺反子表达分析表明，U先导外显子位于5‘非编码区，存在于所有已知的EBNA1转录本中，也存在于EBNA3、4和6mRNAs中，含有IRES。在EBV阳性的淋巴瘤细胞中，EBNA IRES比脑心肌炎病毒IRES更有效地启动翻译。我们认为EBNA IRES构成了一种新的机制，EBV通过该机制调节潜在的基因表达。
Eukaryotic translation can be initiated either by a cap-dependent mechanism or by internal ribosome entry, a process by which ribosomes are directly recruited to structured regions of mRNA upstream of the initiation codon. Here we report the finding of an internal ribosome entry site (IRES) in the untranslated region of the Epstein-Barr nuclear antigen 1 (EBNA1) gene. EBNA1 is the only nuclear protein expressed in all known states of Epstein-Barr virus (EBV) latency and in the virus lytic cycle, and is required for the maintenance of the EBV episome. Using cDNA reporter constructs and in vitro transfection assays, we found that sequences contained in the 5' untranslated region (UTR) of the Fp and Qp initiated EBNA1 mRNA increased the expression level 4-14- fold in different Burkitt lymphoma cell lines. The U leader exon, located within the 5' UTR, included in all known EBNA1 transcripts and also contained in the EBNA3, 4 and 6 mRNAs, was demonstrated by bicistronic expression analyses to contain an IRES. The EBNA IRES initiates translation more efficiently than the encephalomyocarditis virus IRES in EBV-positive lymphoma cells. We propose that the EBNA IRES constitute a novel mechanism, whereby EBV regulates latent gene expression.