Transduction of a murine dominant negative activation transcription factor1 increases cell surface expression of the class I MHC on a human epidermoid tumor cell line
A. Ishizu et al., Transduction of a murine dominant negative activation transcription factor1 increases cell surface expression of the class I MHC on a human epidermoid tumor cell line, INT IMMUNOL, 12(2), 2000, pp. 161-168
The transcription of the MHC class I genes is regulated by interaction of c
is-elements, located in the 5' genomic flanking regions, with sequence-spec
ific trans-factors. We have identified a cis-regulatory element, 5'-TGACGCG
-3', of the H-2D(d) gene. This cyclic adenosine-3',5'-monophosphate regulat
ory element (CRE)-like sequence, named H-2 binding factor 1 (H-2 BF1) bindi
ng motif, is highly conserved among species. In addition, we found that hom
o- and heterodimers of activation transcription factor 1 (ATF-1) and CRE bi
nding protein (CREB) associate with the H-2 BF1 binding motif and activate
transcription of the H-2D(d) gene. Here we demonstrate that a homologue of
ATF-1, originally isolated and designated ATF-1DN, acts as a dominant repre
ssor, blocking the ability of wild-type ATF-1 and CREB to bind to the H-2 B
F1 probe in electrophoretic mobility shift assays (EMSA). We have utilized
this molecule to analyze the participation of the H-2 BF1 complexes, consis
ting of the H-2 BF1 binding motif and ATF-1/CREB trans-factors, in the phys
iological regulation of MHC class I expression in tissue culture cells. A h
uman epidermoid carcinoma cell line, A431, was transfected with ATF-1DN and
clones expressing the gene transcripts were selected. When analyzed in the
EMSA, nuclear proteins prepared from these clones exhibited a decreased sh
ift of the H-2 BF1 probe corresponding to the levels of the ATF-1DN gene ex
pression. Additionally, MHC class I expression of cells with reduced H-2 BF
1 activity was significantly higher than in control cells lacking ATF-1DN.
These findings indicate that in these carcinoma cells, the H-2 BF1 complexe
s negatively regulate the constitutive expression of MHC class I.