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Journal of Virology, January 2000, p. 764-772, Vol. 74, No. 2
Institut für Virologie, Zentrum
für Mikrobiologie und Hygiene, Philipps-Universität
Marburg, 35037 Marburg, Germany
Received 15 June 1999/Accepted 20 October 1999
During the late phase of adenovirus infection, viral mRNA is
efficiently transported from the nucleus to the cytoplasm while most
cellular mRNA species are retained in the nucleus. Two viral proteins,
E1B-55 kDa and E4orf6, are both necessary for these effects. The E4orf6
protein of adenovirus type 5 binds and relocalizes E1B-55 kDa, and the
complex of the two proteins was previously shown to shuttle
continuously between the nucleus and cytoplasm. Nucleocytoplasmic
transport of the complex is achieved by a nuclear export signal (NES)
within E4orf6. Mutation of this signal sequence severely reduces the
ability of the E1B-55 kDa-E4orf6 complex to leave the nucleus. Here,
we examined the role of functional domains within E4orf6 during virus
infection. E4orf6 or mutants derived from it were transiently
expressed, followed by infection with recombinant adenovirus lacking
the E4 region and determination of virus yield. An arginine-rich
putative alpha helix near the carboxy terminus of E4orf6 contributes to
E1B-55 kDa binding and relocalization as well as to the synthesis of
viral DNA, mRNA, and proteins. Further mutational analysis revealed
that mutation of the NES within E4orf6 considerably reduces its ability
to support virus production. The same effect was observed when nuclear
export was blocked with a competitor. Further, a functional NES within E4orf6 contributed to the efficiency of late virus protein synthesis and viral DNA replication, as well as total and cytoplasmic
accumulation of viral late mRNA. Our data support the view that
NES-mediated nucleocytoplasmic shuttling strongly enhances most, if not
all, intracellular activities of E4orf6 during the late phase of
adenovirus infection.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The Nuclear Export Signal within the E4orf6 Protein of Adenovirus
Type 5 Supports Virus Replication and Cytoplasmic Accumulation of
Viral mRNA
*
Corresponding author. Mailing address: Institut
für Virologie, Zentrum für Mikrobiologie und Hygiene,
Philipps-Universität Marburg, Robert Koch Str. 17, 35037 Marburg,
Germany. Phone: 49 6421 28 4318. Fax: 49 6421 28 8962. E-mail:
dobbelst{at}mailer.uni-marburg.de.
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