Lee Y J, Gorski J
Department of Biochemistry, University of Wisconsin-Madison, 53706-1569, USA.
Mol Cell Endocrinol. 1998 Feb;137(1):85-92. doi: 10.1016/s0303-7207(97)00235-9.
We examined noncooperativity of estrogen action by studying the transcription of estrogen receptor (ER) down-regulation in an ER stably transfected cell line (Rat1 + ER). The time-course of the ER transcription rate following 17beta-estradiol (E2) (10 nM) treatment was measured by nuclear run-on assays. ER transcription rates decreased to 40 +/- 3% within 1 h as compared with no treatment and stayed suppressed to 24 h of E2 treatment. The ER transcription rate decrease was noncooperative when measured at 24 h of E2 treatment. This suggested that initial E2 binding to the ER is also a noncooperative process. The Hill coefficients of E2 binding to ER were near unity with an equilibrium dissociation constant of 1-3 nM when measured after a 1 h incubation. These results show that E2 noncooperatively binds ER and down-regulates transcription of ER noncooperatively in intact Ratl + ER cells.
我们通过研究雌激素受体（ER）稳定转染细胞系（Rat1 + ER）中ER下调的转录情况，来检测雌激素作用的非协同性。通过核转录分析测定了17β-雌二醇（E2）（10 nM）处理后ER转录速率的时间进程。与未处理相比，ER转录速率在1小时内降至40±3%，并在E2处理24小时内一直受到抑制。在E2处理24小时时测量，ER转录速率的下降是非协同性的。这表明初始E2与ER的结合也是一个非协同过程。孵育1小时后测量，E2与ER结合的希尔系数接近1，平衡解离常数为1 - 3 nM。这些结果表明，在完整的Ratl + ER细胞中，E2以非协同方式结合ER并以非协同方式下调ER的转录。
