TY - JOUR
T1 - Transactivation via RAR/RXR-Sp1 interaction
T2 - Characterization of binding between Sp1 and GC box motif
AU - Shimada, Jun
AU - Suzuki, Yasuhiro
AU - Kim, Seong Jin
AU - Wang, Pi Chao
AU - Matsumura, Masatoshi
AU - Kojima, Soichi
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2001
Y1 - 2001
N2 - Modulation of Sp1 activity by nuclear receptors is a novel mechanism by which fat-soluble hormones regulate gene expression. We previously established that upon autoinduction of RARs by RA, RARs/RXRs physically interact with Sp1, potentiate Sp1 binding to the GC box motifs, and thus enhance transactivation of the urokinase promoter, which lacks a canonical RAR-responsive element/RXR-responsive element. Here, we examined whether a similar mechanism might participate in transcriptional regulation of other key RA-inducible genes in endothelial cells and characterized binding between Sp1 and GC box motifs. Northern blot analyses showed that in addition to urokinase, after induction of RARs, RA up-regulates GC-rich region-dependent mRNA expression of transglutaminase, TGFβ1, and types I and II TGFβ receptors. RA failed to alter the expression of Sp1 at both mRNA and protein levels. Reporter and gel shift assays and Western blot analyses suggested that either RA-treatment or RAR/RXR-over-expression enhances transactivation of these genes through a GC-rich region and strengthens the affinity of Sp1 to GC box motifs, accompanying a potential conformational change of Sp1 as reflected in its increased immunogenicity. Detailed analyses of the GC box motifs within the urokinase and other promoters indicate that interaction between RAR/RXR and Sp1 does not occur in the presence of nonfunctional GC box motifs containing five tandem purine or pyrimidine bases at the 3′-flanking region of hexanucleotide core sequence. These findings provide insight into the molecular mechanisms underlying RARE/RXRE-independent transactivation of RA-inducible gene promoters.
AB - Modulation of Sp1 activity by nuclear receptors is a novel mechanism by which fat-soluble hormones regulate gene expression. We previously established that upon autoinduction of RARs by RA, RARs/RXRs physically interact with Sp1, potentiate Sp1 binding to the GC box motifs, and thus enhance transactivation of the urokinase promoter, which lacks a canonical RAR-responsive element/RXR-responsive element. Here, we examined whether a similar mechanism might participate in transcriptional regulation of other key RA-inducible genes in endothelial cells and characterized binding between Sp1 and GC box motifs. Northern blot analyses showed that in addition to urokinase, after induction of RARs, RA up-regulates GC-rich region-dependent mRNA expression of transglutaminase, TGFβ1, and types I and II TGFβ receptors. RA failed to alter the expression of Sp1 at both mRNA and protein levels. Reporter and gel shift assays and Western blot analyses suggested that either RA-treatment or RAR/RXR-over-expression enhances transactivation of these genes through a GC-rich region and strengthens the affinity of Sp1 to GC box motifs, accompanying a potential conformational change of Sp1 as reflected in its increased immunogenicity. Detailed analyses of the GC box motifs within the urokinase and other promoters indicate that interaction between RAR/RXR and Sp1 does not occur in the presence of nonfunctional GC box motifs containing five tandem purine or pyrimidine bases at the 3′-flanking region of hexanucleotide core sequence. These findings provide insight into the molecular mechanisms underlying RARE/RXRE-independent transactivation of RA-inducible gene promoters.
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U2 - 10.1210/mend.15.10.0707
DO - 10.1210/mend.15.10.0707
M3 - Article
C2 - 11579201
AN - SCOPUS:0034791419
VL - 15
SP - 1677
EP - 1692
JO - Molecular Endocrinology
JF - Molecular Endocrinology
SN - 0888-8809
IS - 10
ER -