Subdomain structure of the co-chaperone SGTA and activity of its androgen receptor client.
Ligand-dependent activity of steroid receptors is affected by tetratricopeptide repeat (TPR)-containing co-chaperones, such as small glutamine-rich tetratricopeptide repeat-containing alpha (SGTA). However, the precise mechanisms by which the predominantly cytoplasmic TPR proteins affect downstream transcriptional outcomes of steroid signaling remain unclear. In this study, we assessed how SGTA affects ligand sensitivity and action of the androgen receptor (AR) using a transactivation profiling approach. Deletion mapping coupled with structural prediction, transcriptional assays, and in vivo regulation of AR-responsive promoters were used to assess the role of SGTA domains in AR responses. At subsaturating ligand concentrations of ≤ 0.1 nM 5α-dihydrotestosterone, SGTA overexpression constricted AR activity by an average of 32% (P<0.002) across the majority of androgen-responsive loci tested, as well as on endogenous promoters in vivo. The strength of the SGTA effect was associated with the presence or absence of bioinformatically predicated transcription factor motifs at each site. Homodimerizaion of SGTA, which is thought to be necessary for chaperone complex formation, was found to be dependent on the structural integrity of amino acids 1-80, and a core evolutionary conserved peptide within this region (amino acids 21-40) necessary for an effect of SGTA on the activity of both exogenous and endogenous AR. This study provides new insights into the subdomain structure of SGTA and how SGTA acts as a regulator of AR ligand sensitivity. A change in AR:SGTA ratio will impact the cellular and molecular response of prostate cancer cells to maintain androgenic signals, which may influence tumor progression.
Cancer Biology Group, Level 1 Basil Hetzel Institute for Translational Health Research, Freemasons Foundation Centre for Men's Health, Queen Elizabeth Hospital, University of Adelaide, 28 Woodville Road, Woodville South, Adelaide, South Australia 5011, Australia.
Andrew P
AP
Trotta
Eleanor F
EF
Need
Lisa M
LM
Butler
Luke A
LA
Selth
Melissa A
MA
O'Loughlin
Gerhard A
GA
Coetzee
Wayne D
WD
Tilley
Grant
G
Buchanan
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D013196:Dihydrotestosterone / Q000378:metabolism; D017930:Genes, Reporter; D008024:Ligands; D018832:Molecular Chaperones / Q000378:metabolism*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
D002352:Carrier Proteins; D008024:Ligands; D018832:Molecular Chaperones; D011944:Receptors, Androgen; C114575:SGTA protein, human; D014157:Transcription Factors; D013196:Dihydrotestosterone