HCMV通过IE1调控神经干细胞中Hes1表达及节律的机制

Human cytomegalovirus infection (HCMV) infection alters the fate of neural progenitor cell (NPCs), but the involved mechanism remains elucidated. Our group has established the NPCs model for HCMV infection. Using this model, we have proved that HCMV drive NPCs abnormal differentiation toward non-glia/non-neuron cells by dysregulate Notch signaling pathway. As a critical downstream effector of Notch signaling, the oscillated expression of Hes1 plays an important role in fine tuning the proliferation/differentiation of NPCs. We have observed that HCMV infection disrupts the rhythm of Hes1 and downregulates its expression in NPCs, both at both mRNA and protein level. However, the detailed mechanism(s) involved in the downregulation is still be revealed. Our preliminary data indicates that one potential mechanism might be mediated by HCMV-IE1, which possibly prompts Hes1 protein degradation via ubiquitin-proteasome pathway by boosting the ubiquitination of Hes1. The crystal structure have revealed that IE1 protein shares some secondary structure with TRIM protein, which has E3 ubiquitin ligase activity. The immediate early proteins which function as E3 ubiquitin ligase have been reported in some other Herpesviruses, such as ORF61P in Varicella zoster virus (VZV) and ICP0 in Herpes simplex virus 1 (HSV-1). These clues indicate the possibility that HCMV-IE1 also possesses E3 ubiquitin ligase activity. Thus, in the present research project, we will reveal a potential novel mechanism for HCMV infection altering NPCs’ fate, clarify the detailed processes of HCMV-IE1 dysregulating Hes1 expression and rhythm, and also prove the E3 ubiquitin ligase function of IE1.

人巨细胞病毒（HCMV）感染影响神经前体/干细胞（NPCs）的命运，导致其增殖/分化异常，但机制尚不清楚。本实验室建立了HCMV感染的NPCs模型，并利用其证明HCMV通过调控Notch通路，使NPCs异常分化为非胶质非神经元细胞。Hes1是Notch通路重要的下游效应分子，其节律性表达是精确调控NPCs增殖分化的关键。我们在预实验中发现HCMV感染下调了NPCs中Hes1的mRNA和蛋白水平，进而破坏其节律，但机制未明。初步发现HCMV感染NPCs后Hes1泛素化水平及其泛素-蛋白媒体降解均被增强，且IE1可能参与其中。晶体结构分析表明IE1核心区和TRIM蛋白卷曲螺旋结构区具有二级结构相似性，且具E3酶功能的立即早期基因在其他疱疹病毒中已被报道，提示HCMV的IE1可能也具有E3酶活性。因此，本研究将着力阐明HCMV通过IE1调控Hes1的机制，并首次研究HCMV-IE1的E3酶活性。

人巨细胞病毒（HCMV）先天感染是导致儿童神经发育畸形的重要因素，但是其具体机制尚不明确。HCMV感染人胚胎干细胞（NPCs）导致Notch信号通路的紊乱。Hes1作为Notch通路下游重要的效应因子，影响NPC命运和胎脑发育。我们的研究首次报道HCMV的感染下调Hes1的表达，HCMV立即早期蛋白IE1通过泛素蛋白酶体途径下调Hes1。IE1的AA451-475和Hes1互作。此外，我们发现Hes1与NPCs的增殖及神经球的形成等相关，而HCMV的感染通过打破Hes1表达节律及下调Hes1表达，引起胎脑发育异常。我们的研究揭示了HCMV感染下调Hes1导致胎脑发育异常的机制。同时鉴定了HCMV首个E3酶——IE1。同时，我们发现敲除Hes1蛋白通过抑制NPCs的增殖和神经球的形成而扰乱NPCs的细胞命运。这些结果揭示了HCMV感染破坏Hes1节律表达和下调Hes1表达，导致神经发育异常的潜在机制。