In situ structures of the genome and genome-delivery apparatus in a single-stranded RNA virus

Hong Zhou and colleagues provide the first description of genomecapsid interactions in a spherical single-stranded RNA (ssRNA) virus, using the bacteriophage MS2 as a model. Unlike double-stranded DNA viruses that pump their genome into a preformed capsid, ssRNA viruses co-assemble their capsid with their genome. Here the authors determine the MS2 structure at 3.6 resolution and are able to trace around 80 of the backbone of the viral genome, identifying regions that react with the maturation protein and providing insights into the ssRNA capsid co-assembly process.