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J Virol, May 1998, p. 3958-3964, Vol. 72, No. 5
Department of Cellular and Molecular Biology,
Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo
108, Japan
Received 27 October 1997/Accepted 3 February 1998
The expression of human T-cell leukemia virus type 1 (HTLV-1) is
activated by interaction of a viral transactivator protein, Tax, and
cellular transcription factor, CREB (cyclic AMP response element
binding protein), which bind to a 21-bp enhancer in the long terminal
repeats (LTR). THP (Tax-helping protein) was previously determined to
enhance the transactivation by Tax protein. Here we report novel forms
of the human homolog of a member of the Gli oncogene family, Gli2 (also
termed Gli2/THP), an extended form of a zinc finger protein, THP, which
was described previously. Four possible isoforms (hGli2
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Cloning of Novel Isoforms of the Human Gli2
Oncogene and Their Activities To Enhance Tax-Dependent
Transcription of the Human T-Cell Leukemia Virus Type 1 Genome
,
,
,
and
) are formed by combinations of two independent alternative
splicings, and all the isoforms could bind to a DNA motif, TRE2S, in
the LTR. The longer isoforms,
and
, were abundantly expressed in
various cell lines including HTLV-1-infected T-cell lines. Fusion
proteins of the hGli2 isoforms with the DNA-binding domain of Gal4
activated transcription when the reporter contained a Gal4-binding site
and one copy of the 21-bp sequence, to which CREB binds. This
activation was observed only in the presence of Tax. The 21-bp sequence
in the reporter was also essential for the activation. These results
suggest that simultaneous binding of hGli2 and CREB to the respective
sites in the reporter seems to be critical for Tax protein to activate transcription. Consequently, it is probable that the LTR can be regulated by two independent signals through hGli2 and CREB, since the
LTR contains the 21-bp and TRE2S sequences in the vicinity.
*
Corresponding author. Mailing address: Department of
Cellular and Molecular Biology, Institute of Medical Science,
University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
Phone: 81-3-5449-5275. Fax: 81-3-5449-5421. E-mail:
myoshi{at}ims.u-tokyo.ac.jp.
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