Distinct Domains of the RelA NF-κB Subunit Are Required for Negative Cross-talk and Direct Interaction with the Glucocorticoid Receptor

Abstract

The RelA subunit of NF-B and the glucocorticoid receptor mutually repress each others transcriptional activity, thus providing a mechanism for immunosuppression. Deletion analysis of the glucocorticoid receptor has shown that the DNA binding domain and the ligand binding domain are essential components for repression. Here, we show by deletions and point mutations that both the Rel homology domain and the transactivation domains of RelA are required for repression of the transcriptional activity of the glucocorticoid receptor in intact cells. However, only the Rel homology domain of RelA was found to associate with the glucocorticoid receptor in vitro. RelA mutants, not able to repress glucocorticoid receptor activity, but still able to dimerize, behaved as transdominant inhibitors of the repressive activity of wild type RelA. Furthermore, we show that the 13 S E1A protein is able to interfere with the transrepressive activity of RelA. We propose that negative cross-talk between the glucocorticoid receptor and RelA is due to direct interaction via the Rel homology domain of RelA and the DNA binding domain of the glucocorticoid receptor in combination with interference by the transactivation domains of RelA with the transcriptional activity of the glucocorticoid receptor.

The RelA NF-κB subunit and the aryl hydrocarbon receptor (AhR) cooperate to transactivate the c-myc promoter in mammary cells

“…Di erent subunits of the NF-kB/Rel family have been shown to interact with members of other protein families (Bassuk et al, 1997;Shen and Stavnezer, 1998;Wissink et al, 1997;Ferrier et al, 1999;Dickinson et al, 1999;Stein et al, 1993;Raj et al, 1996;Kalkoven et al, 1996;Na et al, 1999). In many of these cases, the associations are fairly speci®c for the RelA subunit, e.g., with glucocorticoid and progesterone receptors (Wissink et al, 1997;Kalkoven et al, 1996) and the YB-1 protein (Raj et al, 1996).…”

“…RelA protein interactions with other transcription factors have been found to lead either to induction (Bassuk et al, 1997;Shen and Stavnezer, 1998) or repression (Wissink et al, 1997;Ferrier et al, 1999) of gene transactivation. In most cases, transcription complex-DNA association involves binding sites for both NF-kB and the partner transcription factor, which are in close proximity to one another (Shen and Stavnezer, 1998;Dickinson et al, 1999).…”

“…In many of these cases, the associations are fairly speci®c for the RelA subunit, e.g., with glucocorticoid and progesterone receptors (Wissink et al, 1997;Kalkoven et al, 1996) and the YB-1 protein (Raj et al, 1996). In contrast, Stat6 (Shen and Stavnezer, 1998), C/EBP (Stein et al, 1993), and retinoid X receptor (Na et al, 1999) functionally interact with both RelA and p50.…”

“…Interestingly, a similar functional interaction of RelA with the progesterone receptor was noted in that p50 and c-Rel subunits failed to a ect the transcriptional activity of the activated PR on a progesterone responsive element construct (Kalkoven et al, 1996). The Rel homology region (RHR) is known to be important both for dimerization of NF-kB/Rel subunits (Grimm and Baeuerle, 1993), as well as for interaction with many of these other proteins (Wissink et al, 1997;Stein et al, 1993). While some AhR domains involved in AhR binding to proteins, such as ARNT, hsp90, and the immunophilin-like ARA-9 protein have been evaluated (Perdew and Brad®eld, 1996;Meyer et al, 1998;Okey et al, 1994;Carver et al, 1998), those required for AhR dimerization with other proteins, e.g.…”

Cross-talk between glucocorticoid receptor and AP-1

“…It is not clear, however, whether the presumed squelching mechanism by which the mutants interfere with GR wild type, is the basis of cross-talk with AP-1. Data with mutants of the genes encoding AP-1 and NF-kB which a ect coactivator binding and cross-talk (SchuÈ le et al, 1990;Wissink et al, 1997), are not yet conclusive as these mutations may have a ected several properties.…”