Sy. Na et al., BCL3, AN I-KAPPA-B PROTEIN, AS A NOVEL TRANSCRIPTION COACTIVATOR OF THE RETINOID-X-RECEPTOR, The Journal of biological chemistry, 273(47), 1998, pp. 30933-30938
We have recently shown that the I kappa B protein I kappa B beta inter
acted with the retinoid X receptor (RXR) and inhibited the g-cis-retin
oic acid (RA)-dependent transactivations (Na, S.-Y., Kim, H.-J,, Lee,
S.-H., Choi, H.-S., Na, D. S., Lee, M.-O., Chung, M., Moore, D. D., an
d Lee, J. W. (1998) J. Biol. Chem. 6, 3212-3215). Herein, we show that
a distinct I kappa B protein Bcl3 also interacts with RXR, as shown i
n the yeast two-hybrid tests and glutathione S-transferase pull-down a
ssays. The Bcl3 interaction involved two distinct subregions of RXR, L
e. constitutive interactions of the N-terminal ABC domains and 9-cis-R
A-dependent interactions of the C-terminal DEF domains. In contrast to
I kappa B beta, Bcl3 did not interact with the AF2 domain of RXR. Bcl
3 specifically interacted with the general transcription factors TFIIB
, TBP, and TFIIA but not with TFIIE alpha in the GST pull-down assays.
TBP and TFIIA,however, were not able to interact with I kappa B beta.
Accordingly, Bcl3 coactivated the 9-cis-RA-induced transactivations o
f RXR, in contrast to the inhibitory actions of I kappa B beta. In add
ition, coexpression of SRC-1 but not p300 further stimulated the Bcl3-
mediated enhancement of the g-cis-RA-induced transactivations of RXR.
These results suggest that distinct I kappa B proteins differentially
modulate the 9-cis-RA-induced transactivations of RXR in vivo.