Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
PLoS Pathog. 2010 Mar 5;6(3):e1000799. doi: 10.1371/journal.ppat.1000799.
The control of RNA stability is a key determinant in cellular gene expression. The stability of any transcript is modulated through the activity of cis- or trans-acting regulatory factors as well as cellular quality control systems that ensure the integrity of a transcript. As a result, invading viral pathogens must be able to subvert cellular RNA decay pathways capable of destroying viral transcripts. Here we report that the Kaposi's sarcoma-associated herpesvirus (KSHV) ORF57 protein binds to a unique KSHV polyadenylated nuclear RNA, called PAN RNA, and protects it from degradation by cellular factors. ORF57 increases PAN RNA levels and its effects are greatest on unstable alleles of PAN RNA. Kinetic analysis of transcription pulse assays shows that ORF57 protects PAN RNA from a rapid cellular RNA decay process, but ORF57 has little effect on transcription or PAN RNA localization based on chromatin immunoprecipitation and in situ hybridization experiments, respectively. Using a UV cross-linking technique, we further demonstrate that ORF57 binds PAN RNA directly in living cells and we show that binding correlates with function. In addition, we define an ORF57-responsive element (ORE) that is necessary for ORF57 binding to PAN RNA and sufficient to confer ORF57-response to a heterologous intronless beta-globin mRNA, but not its spliced counterparts. We conclude that ORF57 binds to viral transcripts in the nucleus and protects them from a cellular RNA decay pathway. We propose that KSHV ORF57 protein functions to enhance the nuclear stability of intronless viral transcripts by protecting them from a cellular RNA quality control pathway.
RNA 稳定性的控制是细胞基因表达的关键决定因素。任何转录本的稳定性都是通过顺式或反式作用的调节因子以及细胞质量控制系统的活性来调节的，这些系统可确保转录本的完整性。因此，入侵的病毒病原体必须能够颠覆能够破坏病毒转录本的细胞 RNA 降解途径。在这里，我们报告卡波济肉瘤相关疱疹病毒（KSHV）ORF57 蛋白与一种独特的 KSHV 多聚腺苷酸化核 RNA，称为 PAN RNA，结合，并保护其免受细胞因子的降解。ORF57 增加了 PAN RNA 的水平，并且对 PAN RNA 的不稳定等位基因的影响最大。转录脉冲测定的动力学分析表明，ORF57 可保护 PAN RNA 免受快速的细胞 RNA 降解过程的影响，但 ORF57 对转录或 PAN RNA 的定位几乎没有影响，这分别基于染色质免疫沉淀和原位杂交实验。使用 UV 交联技术，我们进一步证明 ORF57 在活细胞中直接与 PAN RNA 结合，并且我们表明结合与功能相关。此外，我们定义了一个 ORF57 反应元件（ORE），该元件是 ORF57 与 PAN RNA 结合所必需的，并且足以赋予 ORF57 对异源无内含子的β-珠蛋白 mRNA 的反应，但对其剪接的对应物则没有。我们得出结论，ORF57 在核内与病毒转录本结合，并保护它们免受细胞 RNA 降解途径的影响。我们提出，KSHV ORF57 蛋白通过保护它们免受细胞 RNA 质量控制途径的影响，从而增强无内含子病毒转录本的核稳定性。
Zotero 插件
