Mol. Cell. Biol., 04 1996, 1283-1294, Vol 16, No. 4
T Yamagata, J Nishida, S Tanaka, R Sakai, K Mitani, M Yoshida, T Taniguchi, Y Yazaki and H Hirai
We have isolated a novel cDNA clone encoding interferon (IFN) consensus
sequence-binding protein in adult T-cell leukemia cell line or activated T
cells (ICSAT); this protein is the human homolog of the recently cloned
Pip/LSIRF. ICSAT is structurally most closely related to the previously
cloned ICSBP, a member of the IFN regulatory factor (IRF) family of
proteins that binds to interferon consensus sequences (ICSs) found in many
promoters of the IFN-regulated genes. Among T-cell lines investigated,
ICSAT was abundantly expressed in human T-cell leukemia virus type 1
(HTLV-1)-infected T cells. When the HTLV-1 tax gene was expressed or
phorbol myristake acetate-A23187 stimulation was used, ICSAT expression was
induced in Jurkat cells which otherwise do not express ICSAT. When the
binding of ICSAT to four different ICSs was tested, the relative
differences in binding affinities for those ICSs were determined. To study
the functional role of ICSAT, we performed cotransfection experiments with
the human embryonal carcinoma cell line N-Tera2. ICSAT was demonstrated to
possess repressive function over the gene activation induced by IFN
stimulation or by IRF-1 cotransfection. Such repressive function is similar
to that seen in IRF-2 or ICSBP. However, we have found that ICSAT has a
different repressive effect from that of IRF-2 or ICSBP in some
IFN-responsive reporter constructs. These results suggest that a novel
mechanism of gene regulation by "differential repression" is used by
multiple members of repressor proteins with different repressive effects on
the IFN-responsive genes.
Copyright © 1996, American Society for Microbiology
A novel interferon regulatory factor family transcription factor, ICSAT/Pip/LSIRF, that negatively regulates the activity of interferon- regulated genes
Third Department of Internal Medicine, Tokyo University, Japan.
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