Kranzusch, PhilipSchenk, AndreasRahmeh, AmalRadoshitzky, SheliBavari, SinaWalz, ThomasWhelan, Sean2019-10-052010Kranzusch, P. J., A. D. Schenk, A. A. Rahmeh, S. R. Radoshitzky, S. Bavari, T. Walz, and S. P. J. Whelan. 2010. “Assembly of a Functional Machupo Virus Polymerase Complex.” Proceedings of the National Academy of Sciences 107 (46): 20069–74. https://doi.org/10.1073/pnas.1007152107.0027-84240744-28311091-6490http://nrs.harvard.edu/urn-3:HUL.InstRepos:41483511Segmented negative-sense viruses of the family Arenaviridae encode a large polymerase (L) protein that contains all of the enzymatic activities required for RNA synthesis. These activities include an RNA-dependent RNA polymerase (RdRP) and an RNA endonuclease that cleaves capped primers from cellular mRNAs to prime transcription. Using purified catalytically active Machupo virus L, we provide a view of the overall architecture of this multifunctional polymerase and reconstitute complex formation with an RNA template in vitro. The L protein contains a central ring domain that is similar in appearance to the RdRP of dsRNA viruses and multiple accessory appendages that may be responsible for 5' cap formation. RNA template recognition by L requires a sequence-specific motif located at positions 2-5 in the 3' terminus of the viral genome. Moreover, L-RNA complex formation depends on single-stranded RNA, indicating that inter-termini dsRNA interactions must be partially broken for complex assembly to occur. Our results provide a model for arenavirus polymerase-template interactions and reveal the structural organization of a negative-strand RNA virus L protein.en-USJournal Article2019-10-0510.1073/pnas.1007152107