Measles virus is a highly contagious human pathogen that is experiencing a dangerous resurgence throughout the world, including Europe. Replication of the virus requires encapsidation of the RNA viral genome by the viral nucleoprotein, assembling into molecular suprastructures called nucleocapsids. Researchers at the IBS have developed experimental methods (1) to encapsidate specific RNA sequences in vitro, allowing the high resolution (3.3Å) three dimensional structure determination of these nucleocapsids using cryo-electron microscopy (2). This structure reveals the positions and interactions of the RNA molecule with respect to the nucleoprotein at the highest resolution yet achieved. Using this structure, the importance of specific amino acids in the RNA binding groove for the stability of the nucleocapsids was then demonstrated using Nuclear Magnetic Resonance and site-directed mutagenesis. Crucially, this structure also determines for the first time the register of binding of the RNA genome relative to the nucleocapsid, leading to fundamental new insight into the mechanisms underpinning RNA processing by the RNA polymerase complex.
(1) Self-assembly of measles virus nucleocapsid-like particles : Kinetics and RNA sequence dependence. Milles, Jensen, Communie, Maurin, Schoehn, Ruigrok, Blackledge. Angew Chem Int Ed 55, 9356 (2016)
(2) Assembly and cryo-EM structures of RNA-specific measles virus nucleocapsids provide mechanistic insight into paramyxoviral replication. Desfosses A, Milles S, Jensen MR, Guseva S, Colletier JP, Maurin D, Schoehn G, Gutsche I, Ruigrok RWH, Blackledge M. Proc Natl Acad Sci U S A. ; doi : 10.1073/pnas.1816417116.