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Journal of Virology, October 2000, p. 9507-9514, Vol. 74, No. 20
Department of Biology, Johns Hopkins
University, Baltimore, Maryland 21218,1 and
EMBL, D-69117 Heidelberg, Germany2
Received 2 May 2000/Accepted 11 July 2000
Rous sarcoma virus (RSV), a simple retrovirus, needs to export
unspliced viral RNA from the nucleus to the cytoplasm, circumventing the host cell restriction on cytoplasmic expression of
intron-containing RNA. The cytoplasmic accumulation of full-length
viral RNA is promoted by two cis-acting direct repeat (DR)
elements that flank the src gene; at least one copy of the
DR sequence is necessary for viral replication. We show here that the
DR mediates export of a reporter construct from the nucleus, suggesting
it is a constitutive transport element (CTE). In contrast, human
immunodeficiency virus type 1 (HIV-1) and other complex retroviruses
encode accessory proteins, Rev or Rex, which promote export of
incompletely spliced viral transcripts. This RNA export pathway is CRM1
dependent and can be blocked by the cytotoxic agent leptomycin B. We
show here that DR-mediated export is CRM1 independent, suggesting that
RSV uses a different export pathway from that of HIV-1 and other
complex retroviruses. The simian retroviruses have a CTE which
interacts with the cellular Tap export protein. However, we were unable to detect binding of the RSV DR RNA to Tap, suggesting it may use a
different export pathway from that of the simian retroviruses. These
data suggest that the RSV DR element uses a novel nucleocytoplasmic export pathway.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Rous Sarcoma Virus DR Posttranscriptional Elements
Use a Novel RNA Export Pathway


*
Corresponding author. Mailing address: Department of
Biology, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218. Phone: (410) 516-7289. Fax: (410) 516-7292. E-mail:
KLB{at}jhu.edu.
Present address: Purdue Biopharma L.P., Princeton, NJ 08540.
Present address: NCI-Frederick Cancer Research and Development
Center, Frederick, MD 21702.
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