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J. Virol., Feb 1997, 949-955, Vol 71, No. 2
W Luytjes, H Gerritsma, E Bos and W Spaan
Two temperature-sensitive (ts) mutants of mouse hepatitis virus strain A59,
ts43 and ts379, have been described previously to be ts in infectivity but
unaffected in RNA synthesis (M. J. M. Koolen, A. D. M. E. Osterhaus, G. van
Steenis, M. C. Horzinek, and B. A. M. van der Zeijst, Virology 125:393-402,
1983). We present a detailed analysis of the protein synthesis of the
mutant viruses at the permissive (31 degrees C) and nonpermissive (39.5
degrees C) temperatures. It was found that synthesis of the nucleocapsid
protein N and the membrane protein M of both viruses was insensitive to
temperature. However, the surface protein S of both viruses was retained in
the endoplasmic reticulum at the nonpermissive temperature. This was shown
first by analysis of endoglycosidase H-treated and immunoprecipitated
labeled S proteins. The mature Golgi form of S was not present at the
nonpermissive temperature for the ts viruses, in contrast to wild-type (wt)
virus. Second, gradient purification of immunoprecipitated S after
pulse-chase labeling showed that only wt virus S was oligomerized. We
conclude that the lack of oligomerization causes the retention of the ts S
proteins in the endoplasmic reticulum. As a result, ts virus particles that
were devoid of S were produced at the nonpermissive temperature. This
result could be confirmed by biochemical analysis of purified virus
particles and by electron microscopy.
Copyright © 1997, American Society for Microbiology
Characterization of two temperature-sensitive mutants of coronavirus mouse hepatitis virus strain A59 with maturation defects in the spike protein
Department of Virology, Leiden University, The Netherlands. luytjes@virology.azl.nl
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