Secrets of Hantaan virus assembly solved through high resolution cryo-EM


Currently there is no treatment for the deadly Hantaan infection, however, new information about the virus structure could be used by researchers to design a specific antiviral drug to directly target the virus. Benoît Arragain and his colleagues, at the Grenoble Instruct-ERIC Centre, have produced a high resolution 3D picture of the Hantaan virus nucleocapsid


The Hantaan virus genome is made up of three segments of RNA which are protected by nucleoproteins, together this structure is the nucleocapsid. The nucleoproteins are like building blocks that form around the RNA. Until now, it was not known exactly how the proteins assemble themselves, but it had been hypothesised that it would take 3.6 subunits to make one full rotation. The latest research confirms this earlier prediction as well as showing that each repeating unit of the nucleocapsid is made up of six subunits; two lobes, two arms and two hinges. 



Figure 1 A and B from the paper – The helical structure of the Hantaan nucleocapsid and the six subunits that make up each repeating unit of the nucleoprotein.

(Image used under Creative Commons Attribution License CC BY 4.0 DOI: https://doi.org/10.7554/eLife.43075.003)

Cryo-EM allows researchers to see in detail how the RNA and proteins interact to build the nucleocapsid. Pairing their 3D image of the virus nucleocapsid with information about the electrical charge of the proteins revealed that there is a positively charged groove in which the RNA sits. Usually nucleocapsids are flexible and therefore difficult to study, but Cryo-EM allowed Benoît Arragain and his colleagues to pin-point the structure of the Hantaan virus nucleocapsid with near atomic precision. 

 

Read more: Arragain, B., et al. (2019) High resolution cryo-EM structure of the helical RNA-bound Hantaan virus nucleocapsid reveals its assembly mechanisms. eLife 2019;8:e43075 DOI: 10.7554/eLife.43075