He B, Bowen N T, Minges J T, Wilson E M
Department of Biochemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
J Biol Chem. 2001 Nov 9;276(45):42293-301. doi: 10.1074/jbc.M107492200. Epub 2001 Sep 10.
The androgen receptor undergoes an androgen-specific NH(2)- and COOH-terminal interaction between NH(2)-terminal motif FXXLF and activation function 2 in the ligand binding domain. We demonstrated previously that activation function 2 forms overlapping binding sites for the androgen receptor FXXLF motif and the LXXLL motifs of p160 coactivators. Here we investigate the influence of the NH(2)- and COOH-terminal interaction on androgen receptor function. Specificity and relative potency of the motif interactions were evaluated by ligand dissociation rate and the stability of chimeras of transcriptional intermediary factor 2 with full-length and truncated androgen or glucocorticoid receptor. The results indicate that the androgen receptor activation function 2 interacts specifically and with greater avidity with the single FXXLF motif than with the LXXLL motif region of p160 coactivators, whereas this region of the glucocorticoid receptor interacts preferentially with the LXXLL motifs. Expression of the LXXLL motifs as a fusion protein with the glucocorticoid receptor resulted in loss of agonist-induced receptor destabilization and increased half-time of ligand dissociation. The NH(2)- and COOH-terminal interaction inhibited binding and activation by transcriptional intermediary factor 2. We conclude that the androgen receptor NH(2)- and COOH-terminal interaction reduces the dissociation rate of bound androgen, stabilizes the receptor, and inhibits p160 coactivator recruitment by activation function 2.
雄激素受体在配体结合域的氨基末端基序FXXLF与激活功能2之间发生雄激素特异性的氨基末端和羧基末端相互作用。我们之前证明，激活功能2为雄激素受体FXXLF基序和p160共激活因子的LXXLL基序形成重叠结合位点。在此，我们研究氨基末端和羧基末端相互作用对雄激素受体功能的影响。通过配体解离速率以及转录中介因子2与全长和截短的雄激素或糖皮质激素受体嵌合体的稳定性，评估基序相互作用的特异性和相对效力。结果表明，雄激素受体激活功能2与单个FXXLF基序特异性相互作用，且亲和力高于与p160共激活因子的LXXLL基序区域，而糖皮质激素受体的该区域优先与LXXLL基序相互作用。LXXLL基序与糖皮质激素受体融合蛋白的表达导致激动剂诱导的受体去稳定化丧失以及配体解离半衰期增加。氨基末端和羧基末端相互作用抑制转录中介因子2的结合和激活。我们得出结论，雄激素受体的氨基末端和羧基末端相互作用降低结合雄激素的解离速率，稳定受体，并通过激活功能2抑制p160共激活因子募集。
