X-ray structure of Triatoma virus empty capsid: insights into the mechanism of uncoating and RNA release in dicistroviruses

SANCHEZ- EUGENIA, R; MARTI G.A; DURANA, A; GUERIN, D.M.A.; LÓPEZ-MARIJUAN I

JOURNAL OF GENERAL VIROLOGY

SOC GENERAL MICROBIOLOGY

Lugar: London; Año: 2016 vol. 97 p. 2769 - 2779

0022-1317

In viruses, uncoating and RNA release are two key steps of successfully infecting a target cell.During these steps, the capsid must undergo the necessary conformational changes to allowRNA egress. Despite their importance, these processes are poorly understood in the familyDicistroviridae. Here, we used X-ray crystallography to solve the atomic structure of a Triatomavirus(TrV) empty particle (Protein Data Bank ID 5L7O), which is the resulting capsid after RNArelease. It is observed that the overall shape of the capsid and of the three individual proteins ismaintained in comparison with the mature virion. Furthermore, no channels indicative of RNArelease are formed in the TrV empty particle. However, the most prominent change in the emptyparticle when compared with the mature virion is the loss of order in the N-terminal domain ofthe VP2 protein. In mature virions, the VP2 N-terminal domain of one pentamer is swapped withits twofold related copy in an adjacent pentamer, thereby stabilizing the binding between thepentamers. The loss of these interactions allows us to propose that RNA release may take placethrough transient flipping-out of pentameric subunits. The lower number of stabilizing interactionsbetween the pentamers and the lack of formation of new holes support this model. This modeldiffers from the currently accepted model for rhinoviruses and enteroviruses, in which genomeexternalization occurs by extrusion of the RNA through capsid channels.