A nuclear action of the eukaryotic cochaperone RAP46 in downregulation of glucocorticoid receptor activity.
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Schneikert J, Hubner S, Martin E, Cato AC
A nuclear action of the eukaryotic cochaperone RAP46 in downregulation of glucocorticoid receptor activity.
J Cell Biol. 1999 Sep 6;146(5):929-40.
- PubMed ID
- 10477749 [ View in PubMed]
- Abstract
RAP46 is a eukaryotic cochaperone that associates with several proteins, including the heat shock protein hsp70/hsc70 and the glucocorticoid receptor (GR). Here we show a downregulation of GR-mediated transactivation by RAP46 via a mechanism independent of a cytoplasmic action of this cochaperone. We demonstrate a specific cytoplasmic-nuclear recruitment of RAP46 by the liganded GR that results in inhibition of the transactivation function of the receptor. A repeated sequence motif [EEX(4)](8) at the NH(2) terminus of RAP46 or BAG-1L, a larger isoform of RAP46, is responsible for this downregulation of GR activity. BAG-1, a shorter isoform with only a duplication of the [EEX(4)] sequence, does not inhibit GR activity. The [EEX(4)](8) motif, when linked to an otherwise unrelated protein, abrogated the inhibitory action of endogenous RAP46 on GR-mediated transactivation. The nuclear effects of RAP46 and BAG-1L are specific since GR-mediated inhibition of AP-1 activity was not affected. These studies identify the [EEX(4)](8) sequence as a signature motif for inhibition of GR-mediated transactivation and demonstrate a specific nuclear action of a eukaryotic cochaperone in the regulation of GR activity.