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Journal of Virology, November 2000, p. 10349-10358, Vol. 74, No. 22
Mary Babb Randolph Cancer Center and
Department of Biochemistry, West Virginia University, Morgantown,
West Virginia 26506,1 and HIV Drug
Resistance Program, National Cancer Institute, FCRDC, Frederick,
Maryland 217022
Received 17 April 2000/Accepted 19 August 2000
Retroviral populations exhibit a high evolutionary potential,
giving rise to extensive genetic variation. Error-prone DNA synthesis catalyzed by reverse transcriptase (RT) generates variation in retroviral populations. Structural features within RTs are likely to
contribute to the high rate of errors that occur during reverse
transcription. We sought to determine whether amino acids within
murine leukemia virus (MLV) RT that contact the deoxyribonucleoside triphosphate (dNTP) substrate are important for in vivo fidelity of
reverse transcription. We utilized the previously described ANGIE P
encapsidating cell line, which expresses the amphotropic MLV
envelope and a retroviral vector (pGA-1). pGA-1 expresses the bacterial
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Role of Murine Leukemia Virus Reverse Transcriptase
Deoxyribonucleoside Triphosphate-Binding Site in Retroviral
Replication and In Vivo Fidelity
-galactosidase gene (lacZ), which serves as a
reporter of mutations. Extensive mutagenesis was performed on residues likely to interact with the dNTP substrate, and the effects of these
mutations on the fidelity of reverse transcription were determined. As
expected, most substitution mutations of amino acids that directly
interact with the dNTP substrate significantly reduced viral titers
(>10,000-fold), indicating that these residues played a critical role
in catalysis and viral replication. However, the D153A and A154S
substitutions, which are predicted to affect the interactions with the
triphosphate, resulted in statistically significant increases in the
mutation rate. In addition, the conservative substitution F155W,
which may affect interactions with the base and the ribose, increased
the mutation rate 2.8-fold. Substitutions of residues in the
vicinity of the dNTP-binding site also resulted in statistically
significant decreases in fidelity (1.3- to 2.4-fold). These results
suggest that mutations of residues that contact the substrate dNTP can
affect viral replication as well as alter the fidelity of reverse transcription.
*
Corresponding author. Mailing address: HIV Drug
Resistance Program, NCI FCRDC, Bldg. 535, Rm. 334, Frederick, MD
21702-1201. Phone: (301) 846-1710. Fax: (301) 846-6013. E-mail:
VPATHAK{at}mail.ncifcrf.gov.
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