芳香烴核轉位蛋白ARNT，必須先與另一個具有bHLH/PAS domain的蛋白作用後，才能成為具完整活性的複合體，像是HIF-1α。另外，ARNT曾被報導參與在許多細胞生理功能的角色，像是胚胎發育，胰島β細胞分泌 而與第二類糖尿病代謝的調控，以及細胞增生等。然而，ARNT參與在發炎刺激下的生理功能，對於調控一些基因轉錄的活性和細胞激素刺激下的基因表達，仍是不清楚的。PTX3是一類受前發炎因子刺激，而表現的急性發炎蛋白，在生理上被認為具有古老抗體的功能，包括辨認外來物，活化補體系統，和促進巨噬細胞對免疫原的辨認。另外，PTX3在女性生殖上，參與在卵丘細胞外基質的擴建和促進卵母細胞的成熟及分化，也扮演重要角色。而目前所知，在卵母細胞成熟擴張過程中，EGF調控PTX3的表現，是透過SMAD2/3訊息傳遞路徑;然而對於EGF如何調控PTX3基因轉錄上的表達仍是未知的。所以，我們便利用子宮頸上皮癌HeLa細胞株，觀察EGF刺激PTX3基因表現的調控情形。接著，使用ARNT siRNA干擾技術，發現EGF所誘導PTX3啟動區的活性及mRNA表現，都有抑制的現象。更進一步地，發現不管是在時間或劑量上，大量表現ARNT蛋白都會活化該啟動區的表現，證實了ARNT可以透過轉錄層次來調控該基因的表達。而為了確認ARNT所調控的PTX3基因表達，是透過PTX3啟動子上哪個結合位。首先，我們將PTX3啟動區段切，來分析啟動區上具有ARNT反應的區段。所以，在利用AP-1位置點突變試驗方式後，發現AP-1位置有部份負責ARNT參與在PTX3基因調控表達。另外，我們也發現AP-1和Sp1位置，對於EGF誘導PTX3啟動子活化皆有貢獻。因此，ARNT很有可能透過與c-Jun、Sp1 的交互作用而參與在EGF所誘導的PTX3基因調控。此研究說明，除了發炎因子會刺激PTX3基因表現外，生長因子EGF的刺激，也能夠調控其表達。對於EGF為何能調控發炎反應PTX3基因的表達，ARNT在其中的角色，提供一個新的解釋機制。

The aryl hydrocarbon receptor nuclear translocator (ARNT) serves as the potential hetero-dimeric partner for bHLH-PAS proteins such as hypoxia-inducible factor-1α (HIF-1α). In addition, ARNT has been reported to involve widely in many cellular events, such as embryonic development, pancreatic β-cell function in the regulation of type Ⅱ diabetes and cell proliferation. However, the role of ARNT in the regulation of transcriptional activity and gene expression of cytokines, which cellular biological function involved in the inflammation, is not clear. Pentraxin 3 (PTX3) is an acute phase pro-inflammatory protein, which acts as a functional ancestor of antibodies, recognizing microbes, activating complement system, and facilitating pathogen recognition by phagocytes. Also, PTX3 is essential in female fertility because it participates in cumulus matrix expansion and facilitates the oocyte maturation and development. We know so far that EGF regulates PTX3 gene expression is through the SMAD2/3 signaling pathway. However, the signaling molecules involved in EGF-responsive PTX3 gene expression are not fully clarified. Here, we find EGF-stimulated PTX3 gene expression in the cervical cancer cell line. Also, ARNT small interfering RNA (siRNA) inhibits the promoter activity and the mRNA level of PTX3 in EGF-treated HeLa cells. Furthermore, over-expression of ARNT induces the PTX3 promoter activity in a time- and dose-dependent manner. To characterize the binding sites located in PTX3 promoter which are essential for ARNT-regulated gene expression, we use truncated promoter fragments of PTX3 to analyze the ARNT-responsive regions. In addition, to further confirm AP-1 site involved in the ARNT-activated hPTX3 promoter activity, DNA construct with mutation of AP1-binding site was used. Also, we find that AP-1 and Sp1 sties play a major role for the EGF inducibility of the gene. Thus, we raise the hypothesis that ARNT may co-operate with c-Jun or Sp1 in the EGF induction of PTX3 gene transcription. Taken together, our study will clarify the potential role of ARNT in the regulation of PTX3 gene expression under normoxic condition and provide an additional mechanism in considering the EGF factor as a regulator to control the PTX3 expression, but not only the pro-inflammatory mediators in physiological condition.

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