Essential role of the unusual DNA-binding motif of BAG-1 for inhibition of the glucocorticoid receptor.
The co-chaperone BAG-1 is involved in the regulation of steroid hormone receptors, including the glucocorticoid receptor (GR). More recently, BAG-1 was found in the nucleus where it decreases GR transactivation. Moreover, nonspecific DNA binding of BAG-1 has been reported. We discovered that of the N-terminal part of BAG-1M, the first 8 amino acids are sufficient for DNA binding, containing a stretch of three lysines and a stretch of three arginines. Changing the spacing between these stretches had no effect on DNA binding. Surprisingly, this small, nonsequence-specific DNA binding domain was nonetheless necessary for the inhibitory function of BAG-1 for GR-dependent transcription, whereas the following serine- and threonine-rich E(2)X(4) repeat domain was not. Mutational analysis of these two domains revealed that only mutants retaining DNA binding capability were able to down-regulate GR-mediated transactivation. Intriguingly, lack of DNA binding could not be functionally rescued by BAG-1M harboring a point mutation abolishing interaction with hsp70. Thus, DNA binding and hsp70 interaction are required in cis. We propose that the nonsequence-specific DNA-binding protein BAG-1 acts at specific chromosomal loci by interacting with other proteins.
Schmidt
Ulrike
U
Max Planck Institute of Psychiatry, Kraepelinstrasse 10, D-80804 Munich, Germany.
Wochnik
Gabriela M
GM
Rosenhagen
Marcus C
MC
Young
Jason C
JC
Hartl
F Ulrich
FU
Holsboer
Florian
F
Rein
Theo
T
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D006801:Humans; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors