Exploring the hook-into-groove interaction of the herpesviral nuclear egress complex in a quest towards novel anti-herpesviral inhibitors

• Applicants: Professorin Dr. Susanne Aileen Funke; Professor Dr. Yves André Muller; Professor Dr. Heinrich Sticht
• Subject Area: Structural Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497739266

Common to all herpesviruses is the preassembly of the virions in the nucleus with the final maturation occurring in the cytosol. Due to size constraints, these capsids cannot migrate from the nucleus to the cytosol via the nuclear pores but rely for the transfer on a herpes virus-specific mechanism, named nuclear egress. This process is initiated by the formation of the core nuclear egress complex (core NEC) between two viral proteins. In the previous funding period, we structurally and functionally characterized the core NECs of three prototypical human herpesviruses, namely from α-herpesvirus varicella zoster (VZV), β-herpesvirus human cytomegalovirus (HCMV) and the gamma-herpesvirus Epstein-Barr virus (EBV).Herpesvirus infections are associated with numerous life-threatening diseases; however, vaccines are missing for example for HCMV and EBV. Available drugs are associated with toxicity and bioavailability issues and are under the continuous thread of the emergence of drug resistance or vaccine escape mutations. Hence, research that explores novel herpesvirus drug targets such as the herpesvirus core NEC is highly welcome. A hallmark of all NEC complexes is the so-called hook-into-groove interaction, with one protein forming a groove-like surface onto which a hook-like contiguous segment of thirty residues from the second protein binds. This interaction motif accounts for about 80% of the total number of interactions formed between the proteins in the complex. Because of the contiguous nature of the hook epitope, the hook-into-groove interaction shows significant promise as a target for the development of antiherpesviral drugs.In the present proposal, we will build on our previous in-depth characterization of the three prototypical NECs and explore the synergistic potential of molecular evolution techniques (phage display and splitGFP reassembly) and computational techniques (computational protein design and bioinformatics exploration of NEC sequence co-evolution) to identify novel and potentially smaller peptides that can substitute for the hook segment in the core NEC and thus inhibit NEC formation. Eventually, these could be transformed into peptidomimetics and ultimately into inhibitory small molecules. Such an approach has proven extremely successful in case of proteinases of medical interest (e. g. HIV protease inhibitors). The same strategy will however require a significant research effort in case of herpesviral NEC inhibitors. The outlined research draws on the combined expertise of the three applicants and two external cooperators, namely Prof. Jutta Eichler (FAU, peptide synthesis, competitive binding assays) and Prof. Manfred Marschall (FAU, virology, colocalization imaging, virus propagation assays). This group has extensively collaborated in the past and in particular, on the successful exploration of the NEC.

• DFG Programme: Research Grants