Targeting the RNA helicase, UAP56: understanding KSHV RNA processing mechanisms to novel antiviral approaches

点击翻译按钮获取中文摘要

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus required for the development of Kaposi's sarcoma (KS) and is also associated with two lymphoproliferative disorders; primary effusion lymphoma and multicentric Castleman's disease. At present, there are no specific KSHV antivirals or vaccines and current treatments for KSHV-associated diseases are not targeted relying on rebuilding the immune system and using cytotoxic agents. As KS is an AIDS-defining disease, controlling HIV/AIDS using regulated immune reconstitution has been investigated as a possible treatment for KS. Although, even with effective Antiretroviral Therapy (ART) and well-controlled HIV infection, many patients still develop progressive KS. Consequently, specific, efficacious anti-KS therapies are still urgently needed. These antivirals would significantly enhance current treatments by (a) working in combination with ART, (b) inhibiting KSHV replication associated with transplant immunosuppression or (c) clearing the latently-infected reservoir by reactivating the virus and simultaneously blocking lytic infection.Like all herpesviruses KSHV has two distinct life cycles, a persistence life-long infection (latency) and infectious productive cycle (lytic replication). KSHV lytic replication plays an important part in the pathogenesis of KSHV infection. Therefore, it is essential to study the molecular mechanisms which regulate lytic replication to fully understand KSHV pathogenesis. Moreover, inhibiting KSHV lytic replication may provide an opportunity to develop novel antiviral strategies to inhibit KS formation. We have exciting data demonstrating a novel approach to inhibit KSHV lytic replication. We have identified a small molecule which disrupts an essential virus-host cell interaction, the KSHV ORF57-cellular hTREX interaction, required for the correct processing of viral mRNAs. The ability to specifically disrupt the ORF57-hTREX interaction using this small molecule now presents a novel opportunity to investigate other roles of the ORF57-hTREX interaction in KSHV lytic replication, in particular determining the role of the ORF57-hTREX interaction in enhancing the correct processing of a subset of cellular RNAs, which are also bound by the viral ORF57 protein, and are thought to enhance virus replication. Therefore, we will assess the global changes in cellular mRNA abundance and protein production, using transcriptomic and proteomic approaches, during KSHV latent versus lytic replication in the absence or presence of the small molecule. This will identify cellular transcripts which are stabilised and processed by the ORF57-hTREX interaction. Further analysis will then be performed to examine how ORF57 recognises and binds this subset of cellular transcripts and determine if these cellular transcripts are essential for virus replication.In addition, we wish to further investigate the antiviral potential of the small molecule which disrupts the ORF57-hTREX interaction. We have shown that the small molecule termed, CCT018159, can inhibit KSHV lytic replication and infectious virion production in a cell culture system. The next stage will to be to explore the inhibitory activity of CCT018159 in an appropriate small animal model for human gamma-herpesvirus infection. However, although CCT018159 can be used in this setting, the small molecule has a relatively high metabolic turnover which may reduce its efficacy. Therefore, we will modify the small molecule to enhance its antiviral activity and pharmacokinetic properties using medicinal chemistry approaches. The small molecule and derivatives will then be tested for their ability to inhibit the replication of the murine gamma-2 herpesvirus, murine Gammaherpesvirus 68, in an in vivo setting.