Picornavirus RNA is protected from cleavage by ribonuclease during virion uncoating and transfer across cellular and model membranes.
Picornaviruses are non-enveloped RNA viruses that enter cells via receptor-mediated endocytosis. Because they lack an envelope, picornaviruses face the challenge of delivering their RNA genomes across the membrane of the endocytic vesicle into the cytoplasm to initiate infection. Currently, the mechanism of genome release and translocation across membranes remains poorly understood. Within the enterovirus genus, poliovirus, rhinovirus 2, and rhinovirus 16 have been proposed to release their genomes across intact endosomal membranes through virally induced pores, whereas one study has proposed that rhinovirus 14 releases its RNA following disruption of endosomal membranes. For the more distantly related aphthovirus genus (e.g. foot-and-mouth disease viruses and equine rhinitis A virus) acidification of endosomes results in the disassembly of the virion into pentamers and in the release of the viral RNA into the lumen of the endosome, but no details have been elucidated as how the RNA crosses the vesicle membrane. However, more recent studies suggest aphthovirus RNA is released from intact particles and the dissociation to pentamers may be a late event. In this study we have investigated the RNase A sensitivity of genome translocation of poliovirus using a receptor-decorated-liposome model and the sensitivity of infection of poliovirus and equine-rhinitis A virus to co-internalized RNase A. We show that poliovirus genome translocation is insensitive to RNase A and results in little or no release into the medium in the liposome model. We also show that infectivity is not reduced by co-internalized RNase A for poliovirus and equine rhinitis A virus. Additionally, we show that all poliovirus genomes that are internalized into cells, not just those resulting in infection, are protected from RNase A. These results support a finely coordinated, directional model of viral RNA delivery that involves viral proteins and cellular membranes.
School of Molecular and Cellular Biology & Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, West Yorkshire, United Kingdom.
Elisabetta
E
Groppelli
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America.
Hazel C
0000-0002-2675-771X
HC
Levy
Program in Virology and Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States of America.
Eileen
E
Sun
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America.
Mike
M
Strauss
School of Molecular and Cellular Biology & Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, West Yorkshire, United Kingdom.
Clare
0000-0002-6782-6195
C
Nicol
The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Sarah
S
Gold
Howard Hughes Institute and Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States of America.
Xiaowei
X
Zhuang
The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Tobias J
TJ
Tuthill
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America.
James M
JM
Hogle
School of Molecular and Cellular Biology & Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, West Yorkshire, United Kingdom.
David J
0000-0002-4742-9272
DJ
Rowlands
D006367:HeLa Cells; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008081:Liposomes; D008856:Microscopy, Fluorescence; D010849:Picornaviridae / Q000378:metabolism / Q000472:pathogenicity*; D010850:Picornaviridae Infections / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D014771:Virion / Q000472:pathogenicity*
D008081:Liposomes; D012367:RNA, Viral