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J. Virol., Jan 1998, 467-475, Vol 72, No. 1
K Chandran and ML Nibert
Mammalian reovirus virions undergo partial disassembly of the outer capsid
upon exposure to proteases in vitro, producing infectious subvirion
particles (ISVPs) that lack protein sigma3 and contain protein mu1/mu1C as
endoprotease-generated fragments mu1delta/delta and phi. ISVPs are thought
to be required for two early steps in reovirus infection: membrane
penetration and activation of the particle-bound viral transcriptase
complexes. Genetic and biochemical evidence implicates outer-capsid protein
mu1 in both these steps. To determine whether the cleavage of mu1/mu1C is
relevant to the unique properties of ISVPs, we analyzed the properties of
novel subvirion particles that lacked sigma3 yet retained mu1/mu1C in an
uncleaved but cleavable form. These detergent-plus-protease subvirion
particles (dpSVPs) were produced by treating virions with chymotrypsin in
the presence of micelle-forming concentrations of alkyl sulfate detergents.
Infections with dpSVPs in murine L or canine MDCK cells provided evidence
that the cleavage of mu1/mu1C during viral entry into these cells is
dispensable for reovirus infection. Additionally, dpSVPs behaved like ISVPs
in their capacity to permeabilize lipid bilayers and to undergo
transcriptase activation in vitro, supporting the conclusion that cleavage
of mu1/mu1C to mu1delta/delta and phi during viral entry is not required
for either membrane penetration or transcriptase activation in cells. The
capacity of alkyl sulfate detergents to inhibit the cleavage of mu1/mu1C in
a reversible fashion suggests a specific association between virus particle
and detergent micelles that may mimic virus particle-phospholipid membrane
interactions during reovirus entry into cells.
Copyright © 1998, American Society for Microbiology
Protease cleavage of reovirus capsid protein mu1/mu1C is blocked by alkyl sulfate detergents, yielding a new type of infectious subvirion particle
Department of Biochemistry, College of Agricultural and Life Sciences, and Institute for Molecular Virology, Graduate School, University of Wisconsin-Madison, 53706, USA.
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