Biology of ebolavirus inclusion bodies

• Applicant: Privatdozent Dr. Thomas Hoenen
• Subject Area: Virology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452208680

Ebolaviruses are important human pathogens causing hemorrhagic fevers with high case fatality rates. Unfortunately, while we have recently seen a tremendous progress in the development of treatments, case fatality rates remains high even in treated patients, emphasizing the need for further progress in this field. Therefore, we are interested in better understanding the life cycle of these viruses in order to define targets for novel antivirals, particularly those aimed at the virus-host interface.During infection, ebolavirus proteins accumulate to form structures called inclusion bodies (IBs), which we and others have previously shown to play an essential function in the virus life cycle as sites of viral genome replication and transcription, as well as the assembly of nucleocapsids, which harbor the viral genome inside virus particles. For a number of other non-segmented negative-sense RNA viruses (NNSVs) similar IBs have now been recognized as being liquid organelles, i.e. microenvironments that are not defined by delineating membranes, but are rather held together by liquid-liquid phase separation. Indeed, based on live cell imaging analysis of cells infected with ebolaviruses we have previously found that ebolavirus IBs also display features that suggest a liquid organelle-like character. However, we currently know little about the properties of ebolavirus IBs, what governs their formation, how liquid organelle-like properties may contribute to IB function, or what role specific viral and/or cellular factors play in these processes.In order to better understand both the formation and function of these important structures, we first plan to investigate whether ebolavirus IBs are indeed liquid organelles, based on physical characteristics such as the diffusion coefficient of inclusion body constituents, and susceptibility of IBs to osmotic shock. We will then determine which viral protein-protein and/or protein-RNA interactions contribute to their formation and assess the contributions of the biochemical characteristics of the involved regions. Further, we want to understand how nucleocapsids are exported from inclusion bodies, and particularly whether phase separation due to nucleocapsid condensation plays a role in this process. Finally, since EBOV usurps host proteins for many aspects of its life cycle, we want to characterize the host proteins associated with EBOV IBs using a combination of mass spectrometry-based approaches, and for a selection of the identified factors directly assess the role they play in both the formation and function of IBs. These studies will increase our knowledge of IB biology, which is an emerging topic in virology, not only for ebolaviruses, but also for NNSVs as a whole, and will provide information regarding possible molecular targets for antivirals targeting an essential aspect of the life cycle of these viruses.

• DFG Programme: Research Grants