TY - JOUR
T1 - Fidelity of the RNA-Dependent DNA Synthesis Exhibited by the Reverse Transcriptases of Human Immunodeficiency Virus Types 1 and2 and of Murine Leukemia Virus
T2 - Mispair Extension Frequencies
AU - Bakhanashvili, Mary
AU - Hizi, Amnon
PY - 1992/2/1
Y1 - 1992/2/1
N2 - Human immunodeficiency viruses type 1 and 2 (HIV-1 and HIV-2, respectively) exhibit extensive genetic variations. It was postulated that much of this genetic variability stems from the low fidelity of the reverse transcription step. Both HIV reverse transcriptases (RTs) were shown to be particularly error-prone during the in vitro DNA-dependent DNA synthesis relative to other retroviral RTs. Extension of mismatched 3ʹ-terminig of the primer DNA was shown to be a major determinant in the infidelity of HIV RTs. However, reverse transcriptases generally exhibit dual template specificities. Therefore, we determined in the current study the fidelity of RNA-dependent DNA synthesis catalyzed in vitro by the RTs of HIV-1 and HIV-2 in comparison with that of murine leukemia virus (MLV) RT. Consequently, we examined the ability of these enzymes to extend preformed 3-terminal A·A, A·C, and A·G mispairs by quantitating the amount and length of extended primers in a primer extension assay using ribosomal RNA as a template. The results demonstrate that the three RTs studied exhibit efficient extensions from 3'-terminal mispairs with a specificity of A·C>A·A>A·G. Nevertheless, the HIV RTs are qualitatively as well as quantitatively more error-prone than MLV RT. The mispair extension efficiency appears to be affected mainly by the increase of apparent Km values, rather than by the change in FmM values. In all, it is apparent that polymerization errors produced during the RNA-dependent as well as DNA-dependent DNA synthesis by HIV-1 and HIV-2 RTs might be a major cause for the high mutation frequenciesobserved by these AIDS-causing viruses.
AB - Human immunodeficiency viruses type 1 and 2 (HIV-1 and HIV-2, respectively) exhibit extensive genetic variations. It was postulated that much of this genetic variability stems from the low fidelity of the reverse transcription step. Both HIV reverse transcriptases (RTs) were shown to be particularly error-prone during the in vitro DNA-dependent DNA synthesis relative to other retroviral RTs. Extension of mismatched 3ʹ-terminig of the primer DNA was shown to be a major determinant in the infidelity of HIV RTs. However, reverse transcriptases generally exhibit dual template specificities. Therefore, we determined in the current study the fidelity of RNA-dependent DNA synthesis catalyzed in vitro by the RTs of HIV-1 and HIV-2 in comparison with that of murine leukemia virus (MLV) RT. Consequently, we examined the ability of these enzymes to extend preformed 3-terminal A·A, A·C, and A·G mispairs by quantitating the amount and length of extended primers in a primer extension assay using ribosomal RNA as a template. The results demonstrate that the three RTs studied exhibit efficient extensions from 3'-terminal mispairs with a specificity of A·C>A·A>A·G. Nevertheless, the HIV RTs are qualitatively as well as quantitatively more error-prone than MLV RT. The mispair extension efficiency appears to be affected mainly by the increase of apparent Km values, rather than by the change in FmM values. In all, it is apparent that polymerization errors produced during the RNA-dependent as well as DNA-dependent DNA synthesis by HIV-1 and HIV-2 RTs might be a major cause for the high mutation frequenciesobserved by these AIDS-causing viruses.
UR - http://www.scopus.com/inward/record.url?scp=0026801258&partnerID=8YFLogxK
U2 - 10.1021/bi00154a010
DO - 10.1021/bi00154a010
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AN - SCOPUS:0026801258
SN - 0006-2960
VL - 31
SP - 9393
EP - 9398
JO - Biochemistry
JF - Biochemistry
IS - 39
ER -