Roles and regulation of polyamines during HCMV infection

人类巨细胞病毒（HCMV）在免疫系统功能低下的患者中引起危及生命的疾病，并在子宫内感染的婴儿中引起长期的神经功能缺陷。在HCMV有效复制所需的许多宿主细胞因子中，有一种称为多胺（PAs）的小碱性分子。在其众多的活动中，PAs与细胞中的蛋白质合成机制结合。此外，它们是制造一种名为eIF5A的蛋白质所必需的，这种蛋白质是将氨基酸连接在一起以制造某些蛋白质所必需的。虽然几十年来人们已经知道，PAs对于HCMV的有效繁殖至关重要，并且HCMV感染增加了细胞内PAs的浓度，但需要PAs的原因以及病毒用于确保细胞中有足够数量PAs的机制尚不清楚。对几种控制PAs水平的宿主细胞蛋白的研究中出现的有趣数据表明，PAs和eIF5A可能控制一些HCMV基因的表达，特别是一种名为gpUL4的迷人基因。先前的研究表明，gpUL4的产生受到了极大的抑制，因为当一组特定的氨基酸序列连接在一起时，制造gpUL4的机制被困在信使RNA上。这些和其他结果表明，gpUL4的功能几十年来一直是个谜，它可能有助于控制HCMV感染期间PAs的积累。利用影响gpUL4产生的各种HCMV突变体以及改变PA和eIF5A丰度的遗传和药理学工具，Aim 1将揭示PA和eIF5A是否以及如何改变病毒感染期间的捕获机制。Aim 2将首先测试gpUL4单独在HCMV感染期间调节细胞中PAs浓度的特定假设。另一个实验将测试HCMV是否能在PA水平低的情况下很好地适应繁殖。虽然这些研究的重点是HCMV，特别是gpUL4，但结果将对理解其他可能由类似机制调节的病毒和细胞基因的控制具有广泛的意义。

Human cytomegalovirus (HCMV) causes life-threatening diseases in patients with poorly functioning immune systems as well as long-lasting neurological deficits in infants infected in utero. Among the many host cell factors that are needed by HCMV to replicate efficiently are small alkaline molecules called polyamines (PAs). Among their myriad activities, PAs bind to the protein synthesizing machinery in the cell. As well, they are necessary to make a protein, known as eIF5A, that is required for linking together amino acids to make certain proteins. Although it has been known for decades that the PAs are critical for HCMV to reproduce efficiently and that HCMV infection increases the intracellular concentration of PAs, the reasons why PAs are needed and the mechanisms the virus uses to ensure that there are sufficient amounts of PAs in the cells are unknown. Intriguing data emerging from studies of several host cell proteins that control the levels of PAs suggest that PAs and eIF5A might control expression of some HCMV genes, in particular a fascination one called, gpUL4. Prior studies showed that the production of gpUL4 is greatly repressed because the machinery for making it becomes trapped on the messenger RNA as a particular sequence of amino acids are being linked together. These and other results suggest that gpUL4, the function of which has been enigmatic for decades, might contribute to the control of PAs accumulation during HCMV infection. Using various HCMV mutants that affect the production of gpUL4 along with genetic and pharmacological tools for altering PA and eIF5A abundance, Aim 1 will reveal if and how PA and eIF5A alter the trapping mechanism during viral infection. Aim 2 will first test the specific hypothesis that gpUL4, alone and during HCMV infection, regulates the concentration of PAs in the cells. Another experiment will test whether HCMV can somehow adapt to reproduce well even when PA levels are low. While these studies focus on HCMV, and especially gpUL4, the results will have broad implications for understanding control of other viral and cells genes that are likely regulated by a similar mechanism.