The MARV nucleocapsid complex consists of the genomic RNA and four tightly associated proteins, NP, VP35, VP30, and L ( Figure 5 ). Encapsidation of the viral RNA by the nucleocapsid proteins protects it from both RNase degradation and detection by cellular pattern recognition receptors. Similar to the genomic RNA, the antigenomic RNA, a replicative intermediate, is also encapsidated by the nucleocapsid proteins (see below, 8.2. Transcription and Replication). In contrast, the viral mRNAs are not encapsidated [134] . The nucleocapsid rather than naked RNA serves as the template for viral transcription and replication. In a MARV minigenome system, NP, VP35, and L are essential for transcription and replication [113, 134] . The role of VP30 in MARV transcription and replication is not well understood and the steps in genome amplification that require, or do not require, VP30 are not yet defined.