Cloning of homeobox genes involved in the differentiation of placental cells producing peptide hormones

胎盘绒毛合成激素，如胎盘催乳素(PL)和绒毛膜促性腺激素(CG)。这些肽类激素对维持妊娠和胎儿的发育发育起着重要作用。众所周知，胎盘催乳素和垂体生长激素(GH)的基因具有序列同源性，起源于共同的祖先基因。此外，绒毛膜促性腺激素和垂体促性腺激素(黄体生成素=黄体生成素和卵泡刺激素=卵泡刺激素)和促甲状腺激素(TSH)来自共同的祖先基因。最近的研究表明，GH和TSH的组织特异性表达受POU家族蛋白转录因子Pit-1控制。这一发现使我们推测，Pou家族转录因子(S)可能在胎盘激素的表达中发挥重要作用。探讨胎盘组织是否表达POU家族转录因子。研究Pit-1是否为ex…以人胎盘组织为模板，采用逆转录-聚合酶链式反应(RT-PCR)技术，克隆了人Pit-1基因的编码区。结果表明，胎盘组织中不表达Pit-1基因，提示其他转录因子参与了胎盘组织中PL和CG的表达。RT-PCR检测POU家族的表达表明Oct-1在胎盘组织中表达。结果表明，胎盘中可能存在Pit-1样转录因子，因为Oct-1与Pit-1异源二聚并增强其活性。对其他转录因子的研究发现，Pax-8属于配对结构域蛋白，在胎盘中也有表达。我们已经证明了Pax-8在甲状腺特异表达甲状腺球蛋白基因中起重要作用。结果提示，Pax-8可能参与了胎盘多肽激素的特异性表达。最近的研究表明，转录因子的激活需要翻译后修饰，如磷酸化和还原。例如，Pit-1被磷酸化激活。然而，Pax-8的激活是否也需要翻译后修饰，这一点从未被研究过。我们的研究表明，Pax-8是通过还原而不是通过磷酸化来激活的。由此推测，氧化还原调节对胎盘基因的组织特异性表达具有重要意义。较少

Placental villi synthesize hormones such as plaental lactogen (PL) and chorionic gonadotropin (CG). These peptide hormones play important role for the maintenace of pregnacy and the development and growth of fetus. It is well known that the genes for placental lactogen and pituitary grwoth hormone (GH) share sequence homology and originate from a common ancestral gene. Also chorionic gonadotropin and pituitary gonadotropins (luteinizing hormone=LH and follicle stimulating hormone=FSH) and thyroid stimulating hormone (TSH) originate from a common ancestral gene. Recently, it has been shown that tissue specific expression of GH and TSH is controlled by a transcriptional factor, Pit-1, belonging to POU family protein. This finding lead us to postulate that POU family transcription factor (s) may play important role for the expression of placental hormones. It was thsu investigated whether placental tissue expresses transcription factor belonging to POU family. To study whether Pit-1 is ex … More pressed in human placental tissue or not, a cDNA coding for human Pit-1 was cloned by reverse transcription-polymerase chain reaction (RT-PCR) using pituitary RNA as a template. Using this cDNA,it was revealed that placental tissue does not express Pit-1 gene, suggesting other transcription factor is involved in the placental tissue expression of PL and CG.The search for the expression of POU family by RT-PCR revealed that Oct-1 is expressed in placenta. The result indicated that Pit-1 like transcription factor might be present in placenta since Oct-1 heterodimerizes with Pit-1 and augments its action.Search for other transciption factors revealed that Pax-8, belonging to paired domain protein is also expressed in the placenta. We have demonstrated that Pax-8 play important role for the thyroid specific expression of thyroglobulin gene. The results indicate the possible involvement of Pax-8 for the placental specific expression of peptide hormones. Recently it was demonstrated that post-translational modification such as phosphorylation and reduction is required for the activation of transcription factors. For example, Pit-1 is activated by phosphorylation. However, it has never been studied whether post-translational midification is also required for the activation of Pax-8. Our study revealed that Pax-8 is activated by reduction but not by phosphorylation. It is thus speculated that redox regulation is important for the tissue specific expression of placental genes. Less