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M9640752.TXT
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1996-03-04
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Document 0752
DOCN M9640752
TI Development of zidovudine (AZT) resistance in Jurkat T cells is
associated with decreased expression of the thymidine kinase (TK) gene
and hypermethylation of the 5' end of human TK gene.
DT 9604
AU Wu S; Liu X; Solorzano MM; Kwock R; Avramis VI; Department of
Pediatrics, USC School of Medicine, Childrens; Hospital Los Angeles
90027, USA.
SO J Acquir Immune Defic Syndr Hum Retrovirol. 1995 Jan 1;8(1):1-9. Unique
Identifier : AIDSLINE GENBANK/X54729
AB The T-cell line Jurkat E6-1 was rendered resistant to zidovudine (AZT)
in vitro by exposure to low but gradually increased concentrations of
the drug. Biochemical pharmacology studies of [3H]AZT in the
AZT-resistant T-cell lines showed a significant reduction of AZT
phosphorylation to the mono-, di-, and triphosphate anabolites.
Peripheral blood mononuclear cells (PBMCs) from pediatric patients with
human immunodeficiency virus type 1 (HIV-1) infection showed a similar
pattern of decreased AZT anabolism. Enzymatic studies with purified
thymidine kinase (TK) preparations from these cell lines showed a
gradual decline in Vmax related to their level of resistance to AZT. The
Jurkat/AZT-20 and Jurkat/AZT-100 cells were studied in greater detail
with reverse transcriptase/polymerase chain reaction (RT/PCR) cloned
probes to determine possible molecular mechanisms of resistance to AZT.
TK mRNA was significantly decreased (approximately 5- to 10-fold) in the
AZT-resistant T-cell lines. Southern blot analyses indicated that there
were no major rearrangements or deletions of the TK gene, but the 5' end
of the gene in the AZT-resistant cells is highly methylated when
compared to wild-type cells. No apparent differences were seen in
thymidylate kinase (dTMPk) mRNA levels in the same T-cell lines. Thus
the decreased expression of TK mRNA and resultant TK enzymatic activity
is responsible for the observed reduction in the AZT anabolism in the
resistant T-cell lines. Decreased T-cell TK activity could allow
wild-type, AZT-sensitive HIV-1 to replicate in the presence of
subinhibitory AZT triphosphate (AZT-TP) cellular concentrations enabling
a genetic variant with drug resistance to emerge and outgrow the
AZT-sensitive, wild-type virus.
DE Antiviral Agents/*PHARMACOLOGY Base Sequence Blotting, Southern Cell
Line Cells, Cultured Child Down-Regulation (Physiology) Drug
Resistance DNA/ANALYSIS/ISOLATION & PURIF DNA Primers/CHEMISTRY *Gene
Expression Regulation, Enzymologic Human HIV
Infections/COMPLICATIONS/DRUG THERAPY HIV-1 Leukocytes,
Mononuclear/DRUG EFFECTS/ENZYMOLOGY/VIROLOGY Methylation Molecular
Sequence Data Phosphorylation Polymerase Chain Reaction RNA,
Messenger/BIOSYNTHESIS Support, Non-U.S. Gov't T-Lymphocytes/DRUG
EFFECTS/*ENZYMOLOGY Thymidine Kinase/BIOSYNTHESIS/*GENETICS
Transcription, Genetic Zidovudine/*PHARMACOLOGY JOURNAL ARTICLE
SOURCE: National Library of Medicine. NOTICE: This material may be
protected by Copyright Law (Title 17, U.S.Code).