Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is recognized that high-level resistance to 3'-azido-3'-deoxythymidine (AZT, zidovudine, or Retrovir) is conferred by the presence of four mutations in the human immunodeficiency virus (HIV) reverse transcriptase [RT; deoxynucleoside-triphosphate:DNA deoxynucleotidyltransferase (RNA-directed), EC 2.7.7.49] coding sequence. However, a number of clinical isolates have been observed that exhibit high-level resistance but contain only three of the four identified mutations (Asn-67, Arg-70, and Tyr-215). Construction of a molecular clone with this genotype gave rise to only a partially resistant virus, raising the possibility that an additional mutation existed in some clinical isolates. Using an HIV marker rescue system, we have mapped and identified a fifth mutation conferring resistance to zidovudine, namely, methionine to leucine at codon 41 of HIV RT. An infectious molecular clone containing this mutation together with three previously identified mutations in the RT coding sequence yielded highly resistant HIV after transfection of T cells. Direct detection of the fifth mutation in DNA samples from cocultured peripheral blood lymphocytes by the PCR revealed that it occurred relatively early in the development of zidovudine resistance. However, this mutation was only detected after the appearance of the codon 215 change in the RT coding sequence. Identification of this mutation in addition to the other known mutations conferring resistance enables rapid and direct correlation between an RT genotype and sensitivity of the virus.
 ...
PMID:Fifth mutation in human immunodeficiency virus type 1 reverse transcriptase contributes to the development of high-level resistance to zidovudine. 137 86

There is considerable interest in the potential of human immunodeficiency virus type 1 (HIV-1) to develop drug resistance, especially as 3'-azido-3'-deoxythymidine (Retrovir) is now in widespread clinical use to treat people with AIDS and AIDS-related complex (ARC). To address this possibility, mutations in the HIV reverse transcriptase [deoxynucleoside-triphosphate:DNA deoxynucleotidyltransferase (RNA-directed), EC 2.7.7.49] gene have been introduced by site-directed mutagenesis of cloned constructs in Escherichia coli. Analysis of the recombinant mutant reverse transcriptase from a number of these constructs revealed enzymes that maintained enzyme activity but had a reduced ability to recognize inhibitors such as azidothymidine triphosphate. To assess the infectivity of these mutants, several constructs of proviral HIV clones with mutant reverse transcriptase genes have been made and used to transfect T cells. All five mutants tested have lower infectious potential, suggesting considerable levels of reverse transcriptase activity are required for efficient virus replication. Viable virus recovered from two clones showed decreased sensitivity to the antiviral compound phosphonoformate, thus demonstrating the potential for drug-resistant HIV to replicate. However, although the reverse transcriptase from these mutant viruses showed decreased sensitivity to azidothymidine triphosphate, paradoxically these viruses were hypersensitive to azidothymidine when tested in culture.
 ...
PMID:Infectious potential of human immunodeficiency virus type 1 reverse transcriptase mutants with altered inhibitor sensitivity. 247 34