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J. Virol., Feb 1997, 1181-1190, Vol 71, No. 2
S Ressler, GF Morris and SJ Marriott
The human T-cell leukemia virus type 1 (HTLV-1) transforming protein, Tax,
is a potent transactivator of both viral and cellular gene expression. The
ability of Tax to transform cells is believed to depend on its
transactivation of cellular-growth-regulatory genes. Expression of
proliferating cell nuclear antigen (PCNA) is intimately linked to cell
growth and DNA replication and repair. By testing a series of PCNA promoter
deletion constructs, we have demonstrated that the PCNA promoter can be
transactivated by Tax. The smallest construct that was activated did not
include the ATF/CRE binding site at nucleotide -50, and mutations in the
ATF/CRE element in the context of a larger promoter were still activated by
Tax. In addition, a Tax mutant that is defective for activation of the CRE
pathway retained the ability to activate the -397 promoter construct. When
a series of linker scanner mutations that span the region from nucleotide
-45 to -7 were assayed, mutations in and around a repeat sequence were
found to abolish Tax transactivation. Multimerized copies of either half of
the repeat were Tax responsive. A single protein complex was shown to bind
specifically to the Tax-responsive region, and the binding of this complex
was enhanced in the presence of Tax. These results demonstrate that the
PCNA promoter contains a Tax-responsive element located between nucleotides
-45 and -7 whose sequence is different from those of other, previously
identified Tax-responsive elements. The ability of Tax to activate the PCNA
promoter may play an important role in cellular transformation by HTLV-1.
Copyright © 1997, American Society for Microbiology
Human T-cell leukemia virus type 1 Tax transactivates the human proliferating cell nuclear antigen promoter
Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
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