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J Virol, July 1998, p. 6237-6243, Vol. 72, No. 7
Interdepartmental Graduate Program in
Genetics1 and
Department of
Entomology,2 University of
California, Riverside, California 92521
Received 10 November 1997/Accepted 13 April 1998
Substitution of granulin from the Trichoplusia ni
granulosis virus (TnGV) for polyhedrin of the Autographa
californica multinucleocapsid nuclear polyhedrosis virus
(AcMNPV) yielded a few very large (2 to 5 µm) cuboidal
inclusions in the cytoplasm and nucleus of infected cells. These
polyhedra lacked the beveled edges characteristic of wild-type
AcMNPV polyhedra, contained fractures, and occluded few
virions. Placing a nuclear localization signal (KRKK) in granulin directed more granulin to the nucleus and resulted in more structurally uniform cuboidal inclusions in which no virions were observed. A
granulin-polyhedrin chimera produced tetrahedral occlusions with more
virions than granulin inclusions but many fewer than wild-type
polyhedra. Despite the unusual structure of the granulin and
granulin-polyhedrin inclusions, they interacted with AcMNPV p10 fibrillar structures and electron-dense spacers that are precursors of the polyhedral calyx. The change in inclusion shape obtained with
the granulin-polyhedrin chimera demonstrates that the primary amino
acid sequence affects occlusion body shape, but the large cuboidal
inclusions formed by granulin indicate that the amino acid sequence is
not the only determinant. The failure of granulin or the
granulin-polyhedrin chimera to properly occlude AcMNPV virions suggests that specific interactions occur between polyhedrin and other viral proteins which facilitate normal virion occlusion and
occlusion body assembly and shape in baculoviruses.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Effects of Substituting Granulin or a
Granulin-Polyhedrin Chimera for Polyhedrin on Virion Occlusion and
Polyhedral Morphology in Autographa californica
Multinucleocapsid Nuclear Polyhedrosis Virus
*
Corresponding author. Mailing address: Department of
Entomology, University of California, Riverside, CA 92521. Phone:
909-787-5006. Fax: 909-787-3086. E-mail:
brian.federici{at}ucr.edu.
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