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Journal of Virology, April 2000, p. 3379-3387, Vol. 74, No. 7
Department of Microbiology and
Immunology,1 Department of Cell
Biology,2 and Department of Pediatrics
and the Elizabeth B. Lamb Center for Pediatric
Research,3 Vanderbilt University, Nashville,
Tennessee 37232
Received 28 September 1999/Accepted 21 December 1999
The replicase gene (gene 1) of the coronavirus mouse hepatitis
virus (MHV) encodes two co-amino-terminal polyproteins presumed to
incorporate all the virus-encoded proteins necessary for viral RNA
synthesis. The polyproteins are cotranslationally processed by viral
proteinases into at least 15 mature proteins, including four predicted
cleavage products of less than 25 kDa that together would comprise the
final 59 kDa of protein translated from open reading frame 1a.
Monospecific antibodies directed against the four distinct domains
detected proteins of 10, 12, and 15 kDa (p1a-10, p1a-12, and p1a-15) in
MHV-A59-infected DBT cells, in addition to a previously identified
22-kDa protein (p1a-22). When infected cells were probed by
immunofluorescence laser confocal microscopy, p1a-10, -22, -12, and -15 were detected in discrete foci that were prominent in the perinuclear
region but were widely distributed throughout the cytoplasm as well.
Dual-labeling experiments demonstrated colocalization of the majority
of p1a-22 in replication complexes with the helicase, nucleocapsid, and
3C-like proteinase, as well as with p1a-10, -12, and -15. p1a-22 was
also detected in separate foci adjacent to the replication complexes.
The majority of complexes containing the gene 1 proteins were distinct
from sites of accumulation of the M assembly protein. However, in
perinuclear regions the gene 1 proteins and nucleocapsid were
intercalated with sites of M protein localization. These results
demonstrate that the complexes known to be involved in RNA synthesis
contain multiple gene 1 proteins and are closely associated with
structural proteins at presumed sites of virion assembly.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Four Proteins Processed from the Replicase Gene
Polyprotein of Mouse Hepatitis Virus Colocalize in the Cell Periphery
and Adjacent to Sites of Virion Assembly
*
Corresponding author. Mailing address: Department of
Pediatrics, Vanderbilt University Medical Center, D7235 MCN, Nashville, TN 37232-2581. Phone: (615) 343-9881. Fax: (615) 343-9723. E-mail: mark.denison{at}mcmail.vanderbilt.edu.
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