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Journal of Virology, September 1999, p. 7474-7488, Vol. 73, No. 9
Molecular Genetics Program and Department of
Microbiology and Immunology, Wake Forest University School of
Medicine, Wake Forest University, Winston-Salem, North Carolina
27157-1064
Received 3 March 1999/Accepted 11 June 1999
Adenoviruses bearing lesions in the E1B 55-kDa protein (E1B 55-kDa)
gene are restricted by the cell cycle such that mutant virus growth is
most impaired in cells infected during G1 and least
restricted in cells infected during S phase (F. D. Goodrum and
D. A. Ornelles, J. Virol. 71:548-561, 1997). A similar
defect is reported here for E4 orf6-mutant viruses. An E4 orf3-mutant virus was not restricted for growth by the cell cycle. However, orf3
was required for enhanced growth of an E4 orf6-mutant virus in cells
infected during S phase. The cell cycle restriction may be linked to
virus-mediated mRNA transport because both E1B 55-kDa- and E4
orf6-mutant viruses are defective at regulating mRNA transport at late
times of infection. Accordingly, the cytoplasmic-to-nuclear ratio of
late viral mRNA was reduced in G1 cells infected with the
mutant viruses compared to that in G1 cells infected with the wild-type virus. By contrast, this ratio was equivalent among cells
infected during S phase with the wild-type or mutant viruses. Furthermore, cells infected during S phase with the E1B 55-kDa- or E4
orf6-mutant viruses synthesized more late viral protein than did cells
infected during G1. However, the total amount of cytoplasmic late viral mRNA was greater in cells infected during G1 than in cells infected during S phase with either the
wild-type or mutant viruses, indicating that enhanced transport of
viral mRNA in cells infected during S phase cannot account for the
difference in yields in cells infected during S phase and in cells
infected during G1. Thus, additional factors affect the
cell cycle restriction. These results indicate that the E4 orf6 and
orf3 proteins, in addition to the E1B 55-kDa protein, may cooperate to
promote cell cycle-independent adenovirus growth.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Roles for the E4 orf6, orf3, and E1B 55-Kilodalton
Proteins in Cell Cycle-Independent Adenovirus Replication
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1064. Phone: (336) 716-9332. Fax: (336) 716-9928. E-mail: ornelles{at}wfubmc.edu.
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