FOXO1转录因子参与巨细胞病毒复制及致病的分子机制研究

Human cytomegalovirus (HCMV) mainly infects the neural stem/progenitor cells in the central nervous system (CNS) during congenital HCMV infection, and it causes severe developmental diseases in the CNS. Yet its pathogenesis remains elusive. The Fox family transcription factor FOXO is critical for the maintenance of neural stem cells and their differentiation into neurons, thus we speculate it may be involved in HCMV infection and its related diseases. Indeed, our preliminary data revealed that HCMV infection dramatically upregulated the expression of FOXO1, and recruited it to the viral replication compartment (vRC) to facilitate viral gene transcription. RNAi knockdown of FOXO1 significantly reduced viral gene expression and progeny virus production. Furthermore, HCMV infection deregulated the expression of FOXO1-controlled host genes, which may affect the function of host cells and contribute to disease development. We thus propose that HCMV induces and regulates FOXO1 to facilitate virus replication and its pathogenicity. We will test this hypothesis by further studying: (1) the molecular mechanism of FOXO1 induction by HCMV; (2) the molecular mechanism of FOXO1 recruitment into the vRC and facilitating HCMV gene expression; (3) the effect of HCMV mediated deregulation of FOXO1 and its controlled host gene expression on neural stem/progenitor cell maintenance and differentiation. This study will generate novel knowledge in HCMV and host interaction, and will eventually contribute to the development of new approaches to better control HCMV infection and diseases.

人巨细胞病毒（HCMV）在中枢神经系统侵染神经干细胞，先天性感染引起该系统严重疾病，但机理尚未阐明。FOXO调控神经干细胞增殖和分化，可能在HCMV感染和致病中起关键作用。我们前期发现HCMV感染显著上调FOXO1表达，并将其招募到病毒复制中心促进病毒基因转录；RNA干扰下调FOXO1可显著降低病毒基因表达和病毒增殖；还发现HCMV感染影响FOXO1下游宿主基因的表达，可能由此影响病毒复制及被感染细胞的功能。基于上述发现，我们提出HCMV调控FOXO1功能促进病毒复制并参与致病的假说。本课题将围绕该假说深入研究：（1）HCMV上调FOXO1表达的分子机制；（2）HCMV招募FOXO1进入复制中心并调控病毒基因表达的分子机制；（3）HCMV改变FOXO1功能及其下游基因表达对神经干细胞增殖和分化的影响。本研究有望揭示HCMV与宿主相互作用新机制，为建立HCMV疾病防治新方法提供理论基础。

巨细胞病毒（human cytomegalovirus，HCMV）属于疱疹病毒β亚型，能在宿主体内建立终身潜伏感染。裂解期的HCMV会通过靶向关键的宿主因子，为病毒复制提供适宜的细胞內环境。Forkhead box O (FoxO)蛋白是一种重要的细胞转录因子，在细胞周期调控、细胞自噬和凋亡、代谢调控及抵御氧化应激等过程中起着广泛而重要的作用。最近，FoxO在病毒感染和致病中的作用机制也被广泛关注，已报道α和γ亚型的疱疹病毒都能通过调控FoxO功能促进病毒复制或致病。我们研究发现，HCMV在感染宿主细胞时急剧上调FoxO的表达水平，从而保持病毒增殖；而RNA干扰下调FoxO则严重抑制了病毒复制和子代病毒的扩增。进一步研究发现，下调FoxO基本不影响病毒DNA的复制，但会引起病毒部分早期基因和晚期基因转录水平的显著降低。在HCMV感染宿主细胞的晚期，FoxO被招募至细胞核中的病毒复制中心（viral replication compartments，vRCs）发挥功能，从而调控病毒早期和晚期基因的表达。这种调控作用不是通过直接结合病毒基因组DNA，而是通过和其他病毒或宿主转录因子的相互作用产生的。这些结果说明巨细胞病毒调控和利用FoxO实现高效复制，抑制FoxO的功能可能成为抑制HCMV感染的新思路，为针对这一过程的药物设计奠定了基础。