INHIBITION OF THE RNASE H ACTIVITY OF HIV REVERSE-TRANSCRIPTASE BY AZIDOTHYMIDYLATE

被引:58
|
作者
TAN, CK
CIVIL, R
MIAN, AM
SO, AG
DOWNEY, KM
机构
[1] UNIV MIAMI,SCH MED,DEPT MED,MIAMI,FL 33101
[2] UNIV MIAMI,SCH MED,DEPT ONCOL,MIAMI,FL 33101
[3] UNIV MIAMI,SCH MED,DEPT BIOCHEM MOLEC BIOL,MIAMI,FL 33101
关键词
D O I
10.1021/bi00234a001
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The effects of AZTMP and other nucleoside 5'-monophosphates on the RNA-dependent DNA polymerase and RNase H activities of a recombinant HIV reverse transcriptase have been investigated. Both activities are sensitive to inhibition by millimolar concentrations of AZTMP with MgCl2 as divalent cation activator. Substitution of Mn2+ for Mg2+ markedly potentiates the inhibition of RNase H activity by AZTMP, reducing the IC50 from 5 to 0.05 mM. In contrast, Mn2+ does not alter the sensitivity of the RNA-dependent DNA polymerase activity to inhibition by AZTMP. The inhibition of RNase H activity by AZTMP can be reversed by increasing concentrations of the substrate poly(A)/poly(dT), suggesting that AZTMP may compete with the substrate for binding at the active site of RNase H. Other nucleoside 5'-monophosphates do not inhibit RNase H in the presence of Mg2+. However, in the presence of Mn2+, deoxy- and dideoxynucleoside 5'-monophosphates that are complementary to the DNA strand of the heteroduplex substrate are somewhat inhibitory. The RNA-dependent DNA polymerase activity is a slightly inhibited by AZTMP and ddTMP in either Mg2+ or Mn2+, and substitution of Mn2+ for Mg2+ results in inhibition by ddAMP as well. Naturally occurring ribo- or deoxyribonucleoside 5'-monophosphates are not inhibitory at concentrations up to 5 mM. Since AZTTP/inhibits the RNA-dependent DNA polymerase activity of HIV reverse transcriptase at nanomolar concentrations, it is unlikely that the inhibition of this activity by AZTMP plays a significant role in the antiviral effect of AZT. However, the inhibition of the RNase H activity by AZTMP, which can reach millimolar concentrations in vivo, may account for part of the sensitivity of the virus to AZT.
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收藏
页码:4831 / 4835
页数:5
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