Mechanism Of Enterovirus 71 In Inhibiting The Formation Of Classical Stress Granules

Enterovirus 71(EV71)is an important member of the Picornaviridae and the main cause of fatal cases of hand-foot-and-mouth disease.Stress granules(SGs)are non-membrane cytoplasmic compartments,which consist of stalled translation initiation complexes and RNA-binding proteins to regulate the overall intracellular translation and help host go through these stresses.SG in respond to viral infection shut down the overall translational machinery,thus restrain viral replication and spread.Previous studies reported that picornaviral infection could induce SG formation in the early stage but inhibit in the middle and late stage.However,the molecular mechanisms are still ambiguous and controversial.In this study,we analyzed the dynamic characteristics of eight representative RNA-binding proteins of SG in the EV71 infection cycle.These proteins can be divided into three categories according to their ability to form granules:the first are TIA-1,TIA-1R and Sam68 that form stable granules in the whole viral life cycle,the second is PABP that appears significant granulation in the early phase but disperses in the late phase,the third are G3BP,eIF4A,eIF4G and eIF4E that appear weak granulation in the immediate early phase and totally inhibited then.Further,we analyzed the first kind granules and found that they were induced by viral 2A protease,formed in a phospho-eIF2a-independent manner and couldnot be disassembled by cycloheximide.They were mRNPs granules containing cellular mRNAs and RNA-binding proteins,but were significantly different from the typical SG,thus we called them aberrant SG(ASG).Later,we observed that EV71 infection inhibited the classical SG formation,which resulted from 2A protease but not 3C protease.Finally,we demonstrated that the protease activity of 2A was essential for classical SG inhibition and ASG induction during EV71 infection.In conclusion,we discovered novel mechanisms that EV71 manipulates the SG dynamics which inhibit typical and induce aberrant stress granules,by 2A protease,which benefits viral translation utmost.