Posttranscriptional control of gene expression

我们的研究重点是基因表达的调控，特别是控制细胞和病毒mRNA表达的机制。信使核糖核酸代谢的一个关键步骤是信使核糖核酸从细胞核到细胞质的运输。由HIV-1研究开创的对逆转录病毒系统的分析揭示了核mRNA输出的一些重要方面，这些研究为控制细胞mRNA和蛋白质运输的机制提供了至关重要的见解。我们正在利用逆转录病毒系统，结合生物化学、功能基因组学和蛋白质组学来识别和研究信使核糖核酸代谢的机制。对大分子转录后调控和核质运输机制的剖析对于理解细胞基因表达和病毒表达的过程是相关的。由于转录后调控是病毒繁殖的重要步骤，我们的研究也集中在对HIV和SIV发病机制中这一调控步骤的理解上。来自我的实验室的最新数据证实，细胞内的PSF蛋白是一个与不同的HIV-1 mRNAs相互作用并抑制其表达的因素，从而抑制病毒的产生。PSF在细胞mRNAs转录后调控中的作用正在研究中。CTE和CTE相关的RNA转运元件及其受体细胞TAP/Nxf1蛋白的鉴定，使我们能够进一步剖析其作用机制。Nxf1也是细胞mRNAs的关键受体，我们证明这一功能在后生动物中是保守的。我们还发现Nxf1与剪接因子U2AF35结合，U2AF35在剪接和mRNA输出之间提供了一种新的联系。我们目前正在研究NXF家族其他成员的作用。与疫苗分部George Pavlakis合作，我们研究了一种新的RNA运输元件RTE。RTE的作用机制仍在研究中，但似乎已经劫持了NXF的转运途径。有趣的是，我们发现RTE和CTE的组合协同增加了低表达的病毒mRNAs的产生。由于这些元件的功能在哺乳动物细胞中是保守的，使用RTE-CTE组合提供了一种简单的方法来将基因表达提高到只有通过更繁琐的RNA优化才能实现的水平。

Our research focuses on the regulation of gene expression, in particular the mechanisms controlling cellular and viral mRNA expression. A critical step in the mRNA metabolism is the transport of the mRNA from the nucleus to the cytoplasm. Analysis of retroviral systems, pioneered by research on HIV-1, have shed light into some important aspects of nuclear mRNA export and these studies have provided critical insight into mechanisms governing cellular mRNA and protein transport. We are utilizing retroviral systems to identify and study mechanisms of mRNA metabolism using a combination of biochemistry, functional genomics, and proteomics. The dissection of the mechanisms of posttranscriptional control and nucleocytoplasmic trafficking of macromolecules are relevant to understand processes involved in cellular gene expression as well as virus expression. Since posttranscriptional regulation is an essential step in virus propagation, our studies also focus on the understanding of this regulatory step in pathogenesis of HIV and SIV. Recent data from my lab identified the cellular PSF protein as a factor interacting with distinct HIV-1 mRNAs and inhibiting their expression, hence virus production. The role of PSF in the posttranscriptional regulation of cellular mRNAs is under investigation. The identification of CTE and CTE-related RNA transport elements as well as their receptor, the cellular TAP/NXF1 protein, enabled us to further dissect its mechanism of function. NXF1 is also the key receptor for cellular mRNAs, and we demonstrated that this function is conserved in metazoa. We also found that NXF1 binds to the splicing factor U2AF35 which provides a novel link between splicing and export of mRNA. We are currently examining the role of the other members of the NXF family. In collaboration with George Pavlakis (Vaccine Branch), we study a novel RNA transport element RTE. The mechanism of function of RTE is still under investigation but it appears that RTE has hijacked the NXF transport pathway. Interestingly, we found that a combination of RTE and CTE synergistically increases production of poorly expressed viral mRNAs. Since the function of these elements is conserved in mammalian cells, the use of the RTE-CTE combination provides a simple method to improve gene expression to levels otherwise only achieved via more cumbersome RNA optimization.