Dissecting the mechanism of herpesvirus genome packaging

PROJECT SUMMARY Human herpesviruses can cause congenital birth defects in neonates and a wide range of disease in humans, with particularly devastating effects in immunocompromised individuals. Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma and other cancers, with high prevalence in sub- Saharan Africa. There is no cure for any herpesvirus; most existing antivirals target a single viral process and can lead to resistance mutations. The recent development of a herpesviral packaging inhibitor highlights the viral genome packaging machinery as an attractive target for novel antivirals. The herpesviral packaging machinery is conceptually similar to that of bacteriophages, yet it has additional complexities that include factors of unknown function. In this proposal, I outline my vision to understand the molecular mechanism of herpesvirus packaging. I will determine the function of an essential factor in herpesvirus packaging that has long evaded mechanistic dissection using state-of-the-art proteomics and microscopy approaches. I will also develop a new strategy to apply deep mutational scanning approaches to herpesviral proteins. In parallel, I will determine the structure of the KSHV terminase, the viral molecular motor that packages the viral genome into the nascent capsid. I will then reconstitute the essential components of the KSHV packaging machinery and use these to develop an in vitro packaging assay. This assay will be leveraged to screen for new antivirals and determine the molecular underpinnings of existing drugs that target the packaging machinery. The proposed studies will build a foundation to address long-standing, fundamental questions in DNA virus packaging and understand the mechanism of anti-herpesvirals.