The Role of Apc and beta-Catenin in Cell Regulation and

一氧化氮（NO）是一种促炎信号因子，对PGHS-2（又名考克斯-2）的调节在多个水平上发生。使用条件永生化小鼠结肠上皮细胞对比Apc基因型，我们表明NOS II和NO供体增加了考克斯-2表达，NO供体增加了β-连环蛋白：Tcf/LEF：DNA复合物的形成。这种作用的机制与E-钙粘蛋白的降解和与质膜结合的β-连环蛋白的释放有关。尽管这种NO启动的β-连环蛋白依赖性作用与考克斯-2表达增加相关，但缺乏直接激活考克斯-2启动子的证据。我们现在已经表明，β-连环蛋白信号增加了PEA 3的表达，PEA 3是转录因子Ets家族的成员，并且PEA 3激活了考克斯-2启动子。在一个考克斯-2启动子荧光素酶模型转染了各种转录因子，我们发现PEA 3协同作用与p300显着诱导考克斯-2启动子活性。从NO供体外源性递送或从转染的iNOS内源性产生的一氧化氮增强了转染的PEA 3/p300的考克斯-2启动子活性。用c-jun、β-连环蛋白、TCF-4或各种转录因子组合未观察到NO的刺激，但仅限于PEA 3/p300。这些研究表明，NO在几个水平上刺激考克斯-2的表达。它激活释放β-连环蛋白的金属蛋白酶，增加其信号传导，从而增加PEA 3的表达。此外，NO增加PEA 3与p300组合的转录活性。我们将继续研究这种相互作用的机制，因为p300不仅作为转录因子的共调节因子，而且还通过其组蛋白乙酰化酶活性提供了一种表观遗传调节机制。

The regulation of PGHS-2 (aka COX-2) by nitric oxide (NO), a proinflammatory signaling factor, occurs at several levels. Using conditionally immortalized murine colonic epithelial cells contrasting in Apc genotype, we have shown that NOS II and NO donors increased COX-2 expression and NO donors increased the formation of beta-catenin: Tcf/LEF:DNA complexes. The mechanism of this effect is linked to the degradation of E-cadherin and release of beta-catenin bound to plasma membranes. Although this NO-initiated, beta-catenin-dependent effect was associated with increased expression of COX-2, evidence of direct activation of the COX-2 promoter was lacking. We now have shown that beta-catenin signaling increases the expression of PEA3, a member of the Ets family of transcriptional factors and that PEA3 activates the COX-2 promoter. In a COX-2 promoter luciferase model transfected with a variety of transcriptional factors, we showed that PEA3 acting synergistically with p300 markedly induced COX-2 promoter activity. Nitric oxide, delivered exogenously from NO donors or produced endogenously from transfected iNOS, augmented COX-2 promoter activity of transfected PEA3/p300. The stimulation by NO was not seen with c-jun, beta-catenin, TCF-4, or with various combinations of transcriptional factors, but was limited to PEA3/p300. These studies suggest that NO acts at several levels to stimulate COX-2 expression. It activates metalloproteinases which releases beta-catenin, increases its signaling and thereby increases the expression of PEA3. Furthermore, NO increases the transcriptional activity of PEA3 in combination with p300. We will pursue the mechanisms of this interaction because p300 not only acts as a co-regulator with transcriptional factors but also provides a mechanism for epigenetic modulation through its histone acetylase activity.