Retinoblastoma (Rb) protein pathway in human cytomegalovirus infected cells

描述(申请人提供)：人巨细胞病毒(HCMV)是一种普遍存在的重要病原体，刺激细胞周期进展。HCMV是心血管疾病的辅助因子，具有显著的增殖性成分，如冠状动脉再狭窄和移植血管硬化症(TVS)，并可能在某些类型的癌症中发挥作用，最明显的是恶性胶质瘤(GBM)。细胞的增殖和转化受视网膜母细胞瘤抑癌基因家族(Rb、p107和p130)的调控。Rb蛋白与E2F转录因子家族一起调节DNA复制所需的细胞基因的表达，如从头途径的核苷酸生物合成酶(NBE)，以及参与伤口愈合和血管生成的分泌因子。当Rb蛋白的低磷酸化形式与E2F蛋白结合时，E2F反应基因的表达受到抑制。低磷酸化的Rb蛋白的降解或其过度磷酸化破坏了它们与E2F的复合体，从而允许游离的E2F激活基因表达。HCMV编码四种调节RB-E2F途径的蛋白质：PP71、IE1、IE2，以及这一应用的焦点UL97。由于HCMV与增殖性疾病相关，并编码多种调节Rb-E2F途径的蛋白，我们推测Rb-E2F途径在HCMV的复制和致病过程中起关键作用。在这里，我们建议探讨RB、E2F和UL97蛋白在HCMV感染过程中的作用。UL97是保守的疱疹病毒蛋白激酶(CHPKs)家族中的一员，它直接磷酸化Rb蛋白并使其失活，导致细胞内E2F反应基因的诱导。我们推测其中一些E2F反应基因产物(NBE)负责UL97介导的对病毒DNA复制的刺激。我们进一步推测，UL97(分泌型伤口愈合和血管生成因子)诱导的其他E2F反应基因产物可能反过来又部分地导致了与HCMV感染相关的增殖性病理，如再狭窄、TVS和GBMS。该项目的长期目标是确定UL97和其他HCMV蛋白使RB失活如何在细胞自主和非细胞自主方式下影响细胞周期进展、HCMV复制和病毒致病，并利用这些信息设计治疗与HCMV感染相关的增殖性疾病的方法。PHS 398/2590(05/01版)第1页续格式页 与公共卫生相关：一些病毒会导致癌症，这是一种细胞生长不受控制的疾病。人类巨细胞病毒(HCMV)感染几乎所有人，导致严重疾病，特别是新生儿和移植患者，并可能在许多不同类型的癌症中发挥作用。我们正在研究巨细胞病毒是如何促使细胞生长的，希望能找到阻止这一过程的药物，并将其用于抗病毒和抗癌治疗。

DESCRIPTION (provided by applicant): Human cytomegalovirus (HCMV) is a ubiquitous and significant pathogen that stimulates cell cycle progression. HCMV is a cofactor for cardiovascular diseases with significant proliferative components such as coronary restenosis and transplant vascular sclerosis (TVS), and may play a role in certain types of cancers, most notably, malignant gliomas (GBMs). Cellular proliferation and transformation is regulated by the retinoblastoma family of tumor suppressors (Rb, p107, and p130). The Rb proteins, in conjunction with the E2F family of transcription factors, regulate the expression of cellular genes required for DNA replication such as nucleotide biosynthetic enzymes (NBEs) of the de novo pathway, as well as secreted factors involved in wound healing and angiogenesis. The expression of E2F-responsive genes is inhibited when the hypophosphorylated forms of the Rb proteins are bound to the E2F proteins. Degradation of the hypophosphorylated Rb proteins, or their hyperphosphorylation disrupts their complexes with E2F, thus allowing free E2F to activate gene expression. HCMV encodes four proteins that modulate the Rb-E2F pathway: pp71, IE1, IE2, and the focus of this application, UL97. Because HCMV is associated with proliferative diseases and encodes multiple proteins that modulate the Rb-E2F pathway, we hypothesize that the Rb-E2F pathway plays a critical role in HCMV replication and pathogenesis. Here we propose to explore the roles of the Rb, E2F, and UL97 proteins during HCMV infection. UL97 is a member of a family of conserved herpesvirus protein kinases (CHPKs) that directly phosphorylates the Rb protein and inactivates it, leading to the induction of cellular E2F-responsive genes. We hypothesize that some of these E2F-responsive gene products (the NBEs) are responsible for the UL97-mediated stimulation of viral DNA replication. We further speculate that other E2F-responsive gene products induced by UL97 (secreted wound healing and angiogenesis factors) may in turn be partially responsible for proliferative pathologies associated with HCMV infection, such as restenosis, TVS, and GBMs. The long-term goal of this project is to determine how Rb inactivation by UL97 and other HCMV proteins impacts cell cycle progression, HCMV replication, and viral pathogenesis in both cell autonomous and non-cell-autonomous manners, and to use this information to design therapies to treat proliferative diseases associated with HCMV infection. PHS 398/2590 (Rev. 05/01) Page 1 Continuation Format Page PUBLIC HEALTH RELEVANCE: Some viruses cause cancer, a disease of uncontrolled cellular growth. Human cytomegalovirus (HCMV) infects almost everyone, causes severe disease especially in newborn infants and transplant patients, and may play a role in many different types of cancer. We are studying how HCMV causes cells to grow in the hopes of finding drugs to stop that process, and that could be used as anti-viral and anti-cancer treatments.