Receptor Biology Section, Laboratory of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
J Biol Chem. 2010 Jan 22;285(4):2676-85. doi: 10.1074/jbc.M109.043471. Epub 2009 Nov 17.
Estrogen enables uterine proliferation, which depends on synthesis of the IGF1 growth factor. This proliferation and IGF1 synthesis requires the estrogen receptor (ER), which binds directly to target DNA sequences (estrogen-responsive elements or EREs), or interacts with other transcription factors, such as AP1, to impact transcription. We observe neither uterine growth nor an increase in Igf1 transcript in a mouse with a DNA-binding mutated ER alpha (KIKO), indicating that both Igf1 regulation and uterine proliferation require the DNA binding function of the ER. We identified several potential EREs in the Igf1 gene, and chromatin immunoprecipitation analysis revealed ER alpha binding to these EREs in wild type but not KIKO chromatin. STAT5 is also reported to regulate Igf1; uterine Stat5a transcript is increased by estradiol (E(2)), but not in KIKO or alpha ERKO uteri, indicating ER alpha- and ERE-dependent regulation. ER alpha binds to a potential Stat5a ERE. We hypothesize that E(2) increases Stat5a transcript through ERE binding; that ER alpha, either alone or together with STAT5, then acts to increase Igf1 transcription; and that the resulting lack of IGF1 impairs KIKO uterine growth. Treatment with exogenous IGF1, alone or in combination with E(2), induces proliferation in wild type but not KIKO uteri, indicating that IGF1 replacement does not rescue the KIKO proliferative response. Together, these observations suggest in contrast to previous in vitro studies of IGF-1 regulation involving AP1 motifs that direct ER alpha-DNA interaction is required to increase Igf1 transcription. Additionally, full ER alpha function is needed to mediate other cellular signals of the growth factor for uterine growth.
雌激素使子宫增殖，这依赖于 IGF1 生长因子的合成。这种增殖和 IGF1 合成需要雌激素受体（ER），它直接与靶 DNA 序列（雌激素反应元件或 EREs）结合，或与其他转录因子如 AP1 相互作用，以影响转录。我们观察到具有 DNA 结合突变的 ERα（KIKO）的小鼠既没有子宫生长也没有 Igf1 转录增加，这表明 Igf1 调节和子宫增殖都需要 ER 的 DNA 结合功能。我们在 Igf1 基因中鉴定了几个潜在的 EREs，染色质免疫沉淀分析显示 ERα 在野生型但不在 KIKO 染色质中结合这些 EREs。STAT5 也被报道调节 Igf1；雌激素（E2）增加子宫 Stat5a 转录，但在 KIKO 或α ERKO 子宫中则没有，表明 ERα 和 ERE 依赖性调节。ERα 结合到潜在的 Stat5a ERE 上。我们假设 E2 通过 ERE 结合增加 Stat5a 转录；然后 ERα 单独或与 STAT5 一起作用以增加 Igf1 转录；并且由此导致的 IGF1 缺乏会损害 KIKO 子宫生长。单独或与 E2 联合使用外源性 IGF1 可诱导野生型子宫增殖，但不能诱导 KIKO 子宫增殖，表明 IGF1 替代不能挽救 KIKO 的增殖反应。这些观察结果表明，与涉及 AP1 基序的 IGF-1 调节的先前体外研究相反，增加 Igf1 转录需要直接的 ERα-DNA 相互作用。此外，需要完整的 ERα 功能来介导生长因子对子宫生长的其他细胞信号。
