Forty-Five Years of Marburg Virus Research

Brauburger, Kristina; Hume, Adam J.; Mühlberger, Elke; Olejnik, Judith

The nucleoprotein NP enwraps the genomic and antigenomic RNAs. Replication and transcription activity in a MARV minigenome system depends on the presence of NP [134] . When NP is expressed in the absence of other nucleocapsid proteins, it self-assembles into highly organized helical tubular structures that resemble the nucleocapsids in infected cells, indicating that it is the driving force for nucleocapsid formation [60, 135, 136] . Recently, it has been shown that the conserved 390 N-terminal residues of MARV NP are sufficient to form the helical structure of the nucleocapsid core [60] . Indeed, NP serves as a viral hub protein. It forms interactions with most of the other viral proteins, leading to the subcellular redistribution of these proteins. The strong binding of NP to the nucleocapsid proteins VP35 and VP30 redirects both proteins into NP-derived inclusions [115] . A bipartite coiled-coil motif in the central part of NP has been shown to play an important role for self-assembly and NP-VP35 interaction [137] . As mentioned above, there is also a weak interaction between NP and VP24, leading to the partial relocalization of VP24 into NP-containing inclusions [60, 132] . In addition, NP interacts with VP40, which is important for the transport of newly synthesized nucleocapsids to the plasma membrane [110, 111, 138, 139] . Interestingly, NP contains a C-terminal late domain motif, PSAP, which has been shown to be required for budding. NP recruits Tsg101, a component of the ESCRT I complex, through its late domain motif, leading to enhanced VP40-induced budding [111] .