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Journal of Virology, January 2001, p. 809-820, Vol. 75, No. 2
Department of Microbiology and Immunology,
School of Medicine, West Virginia University, Morgantown, West
Virginia 26506,1 and HIV Drug Resistance
Program, National Cancer Institute, Frederick Cancer Research and
Development Center, Frederick, Maryland 217022
Received 13 July 2000/Accepted 25 October 2000
Homology between the two repeat (R) regions in the retroviral
genome mediates minus-strand DNA transfer during reverse transcription. We sought to define the effects of R homology lengths on minus-strand DNA transfer. We generated five murine leukemia virus (MLV)-based vectors that contained identical sequences but different lengths of the
3' R (3, 6, 12, 24 and 69 nucleotides [nt]); 69 nt is the full-length MLV R. After one round of
replication, viral titers from the vector with a full-length downstream
R were compared with viral titers generated from the other four vectors
with reduced R lengths. Viral titers generated from vectors with R
lengths reduced to one-third (24 nt) or one-sixth (12 nt) that of the wild type were not significantly affected; however, viral titers generated from vectors with only 3- or 6-nt homology in the R region
were significantly lower. Because expression and packaging of the RNA
were similar among all the vectors, the differences in the viral titers
most likely reflected the impact of the homology lengths on the
efficiency of minus-strand DNA transfer. The molecular nature of
minus-strand DNA transfer was characterized in 63 proviruses. Precise
R-to-R transfer was observed in most proviruses generated from vectors
with 12-, 24-, or 69-nt homology in R, whereas aberrant transfers were
predominantly used to generate proviruses from vectors with 3- or 6-nt
homology. Reverse transcription using RNA transcribed from an upstream
promoter, termed read-in RNA transcripts, resulted in most of the
aberrant transfers. These data demonstrate that minus-strand DNA
transfer is homology driven and a minimum homology length is required
for accurate and efficient minus-strand DNA transfer.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.2.809-820.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Effects of Homology Length in the Repeat Region on
Minus-Strand DNA Transfer and Retroviral Replication
*
Corresponding author. Mailing address: HIV Drug
Resistance Program, National Cancer Institute, FCRDC, Room 336, Building 535, Frederick, MD 21702. Phone: (301) 846-1250. Fax: (301)
846-6013. E-mail: whu{at}ncifcrf.gov.
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