Leondires Mark P, Hu Zhang Zhi, Dong Juying, Tsai-Morris Chon Hwa, Dufau Maria L
National Institute of Child Health and Human Development, Section Molecular Endocrinology, Endocrinology and Reproduction Research Branch, National Institutes of Health, Bethesda, MD 20892-4510, USA.
J Steroid Biochem Mol Biol. 2002 Oct;82(2-3):263-8. doi: 10.1016/s0960-0760(02)00184-x.
Human prolactin receptor (hPRLR) expression is regulated by estradiol-17beta (E(2)) in vivo in animal tissues, and in vitro in normal human endometrial cells and in MCF7 human breast cancer cells. The objective of this study was to determine the effect of E(2) on the expression of two recently described hPRLR isoforms with distinct exons-1, hE1(3) and hE1(N1) that are transcribed from the generic hPIII promoter, also present in the rat and mouse, and the human-specific promoter hP(N1), respectively. Also, to determine the effect of estradiol on the hPIII promoter activity in cancer cells. T47D breast cancer cells were examined using quantitative competitive RT-PCR for the level of expression of two alternative non-coding exon-1 transcripts, hE1(3) and hE1(N1) following incubation with E(2) in presence or absence of the E(2) receptor antagonist ICI 182,780. The effects of estradiol were also evaluated in cells transiently transfected with constructs of hPIII promoter luciferase reporter gene. E(2) significantly increased the expression of both hPRLR mRNA transcripts, hE1(3) and hE1(N1). In transfection studies E(2) activated the hPIII promoter. This effect of estradiol was markedly inhibited by coincubation with the E(2) receptor antagonist. Our results demonstrate a stimulatory effect of estradiol on the expression of hPRLR mRNA species with alternative exons-1, hE1(3) and hE1(N1) possibly through activation of their corresponding promoters. The lack of a formal ERE in these promoters suggested that the effect of estradiol is mediated through association of the activated ER with relevant DNA binding transfactor(s). These findings support the role of E(2) in the regulation of hPRLR expression in human breast cancer cell lines.
在动物组织的体内以及正常人类子宫内膜细胞和MCF7人乳腺癌细胞的体外实验中，人催乳素受体（hPRLR）的表达受17β-雌二醇（E₂）调控。本研究的目的是确定E₂对两种最近描述的具有不同外显子1的hPRLR亚型（hE1(3)和hE1(N1)）表达的影响，它们分别从大鼠和小鼠中也存在的通用hPIII启动子以及人特异性启动子hP(N1)转录而来。此外，确定雌二醇对癌细胞中hPIII启动子活性的影响。使用定量竞争性RT-PCR检测T47D乳腺癌细胞在存在或不存在E₂受体拮抗剂ICI 182,780的情况下与E₂孵育后两种替代性非编码外显子1转录本（hE1(3)和hE1(N1)）的表达水平。还在瞬时转染了hPIII启动子荧光素酶报告基因构建体的细胞中评估了雌二醇的作用。E₂显著增加了两种hPRLR mRNA转录本hE1(3)和hE1(N1)的表达。在转染研究中，E₂激活了hPIII启动子。与E₂受体拮抗剂共同孵育可显著抑制雌二醇的这种作用。我们的结果表明，雌二醇可能通过激活其相应启动子对具有替代性外显子1的hPRLR mRNA亚型hE1(3)和hE1(N1)的表达具有刺激作用。这些启动子中缺乏正式的雌激素反应元件（ERE）表明，雌二醇的作用是通过活化的雌激素受体（ER）与相关DNA结合转录因子的结合介导的。这些发现支持了E₂在人乳腺癌细胞系中hPRLR表达调控中的作用。
