Charakterisierung und Funktionsanalyse der Bindungsdomaene für den Kofaktor VP35 der RNA-Polymerase L des Ebola-Virus

Replication and transcription of the RNA genome of the highly pathogenic Ebola virus (EBOV) is based on the reconstitution of active RNA-dependent RNA polymerase complexes consisting of the catalytical subunit of the polymerase L and the polymerase cofactor VP35. For replication and transcription, this complex has to interact with the RNA genome which is tightly encapsidated by NP. The L protein acts as a key-enzyme in this process. In this study, complex formation dependent on the interaction of L and VP35 was investigated. Furthermore, L-deletion mutants were tested for their ability to inhibit EBOV replication and transcription. Coexpression studies revealed that L did not interact with NP directly but was relocalized in NP-derived inclusion bodies by binding to VP35. Further investigations using co-immunoprecipitation assays and immunofluorescence analysis could show that the binding domain for VP35 is located within the aminoterminal part of L between amino acid 280 and 380. Stabilization of this complex occurs by interaction of VP35 with an additional part of L comprising amino acid 240 to 280. L-L complex formation was shown to occur in the absence of VP35 and is mediated by an aminoterminally located binding domain. The homo-oligomerisation domain of L comprises amino acid 1 to 450. Finally, minigenom assays were performed to investigate inhibitory effects of L-deletion mutants on EBOV replication and transcription. Our data suggest that short L-fragments with at least 380 aminoterminal amino acids were able to efficiently block EBOV replication and transcription revealing the VP35 binding site on L as a potential target for the development of antiviral compounds.