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Proc Natl Acad Sci U S A. 2010 Nov 16;107(46):20069-74. doi: 10.1073/pnas.1007152107. Epub 2010 Oct 26.

Assembly of a functional Machupo virus polymerase complex.

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  • 1Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.


Segmented 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.

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