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J. Virol., Mar 1997, 1975-1983, Vol 71, No. 3
I Lemasson, V Robert-Hebmann, S Hamaia, M Duc Dodon, L Gazzolo and C Devaux
To understand the mechanism of p56lck protein downregulation observed in
human T cells infected by human T-cell leukemia virus type 1 (HTLV- 1), we
have investigated the ability of the 3' end of the HTLV-1 genome as well as
that of the tax and rex genes to modulate p56lck protein expression and
p56lck mRNA synthesis. By using Jurkat T cells stably transfected with
constructs that expressed either the 3' end of the HTLV-1 genome (JK
C11-pMTEX), the tax gene (JK52-Tax) or the rex gene (JK9-Rex), we found
that the expression of p40tax (Tax) was sufficient to modulate p56lck
protein expression. Similarly, we found that the expression of the mRNA
which encoded p56lck was repressed in Jurkat T cells which expressed Tax.
This downregulation was shown to be proportional to the amount of tax mRNA
found in the transfected cells, as evidenced by experiments that used cells
(JPX-9) stably transfected with a tax gene driven by a cadmium-inducible
promoter. Furthermore, cadmium induction of Tax in JPX-9 cells transiently
transfected with a construct containing the chloramphenicol
acetyltransferase (CAT) gene under control of the lck distal promoter (lck
DP-CAT) resulted in the downregulation of CAT gene expression. In contrast,
cadmium induction of Tax in JPX-9 cells transiently transfected with a CAT
construct driven by a lck DP with a deletion extending from position -259
to -253 (a sequence corresponding to a putative E-Box) did not modulate CAT
gene expression, suggesting that the effect of Tax on p56lck is mediated
through an E-Box binding protein.
Copyright © 1997, American Society for Microbiology
Transrepression of lck gene expression by human T-cell leukemia virus type 1-encoded p40tax
Laboratoire d'Immunologie des Infections Retrovirales, CNRS ERS 155- INSERM U249, Institut de Biologie, Montpellier, France.
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