Gao Feng-Hou, Wang Qiong, Wu Ying-Li, Li Xi, Zhao Ke-Wen, Chen Guo-Qiang
Department of Pathophysiology, Rui-Jin Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai 200025, China.
Biochem Biophys Res Commun. 2007 May 4;356(2):505-11. doi: 10.1016/j.bbrc.2007.03.009. Epub 2007 Mar 8.
AML1-ETO fusion protein, a product of leukemia-related chromosomal translocation t(8;21), was reported to upregulate expression of connexin-43 (Cx43), a member of gap junction-constituted connexin family. However, its mechanism(s) remains unclear. By bioinformatic analysis, here we showed that there are two putative AML1-binding consensus sequences followed by two activated protein (AP)1 sites in the 5'-flanking region upstream to Cx43 gene. AML1-ETO could directly bind to these two AML1-binding sites in electrophoretic mobility shift assay, but luciferase reporter assay revealed that the AML1 binding sites were not indispensable for Cx43 induction by AML1-ETO protein. Conversely, AP1 sites exerted an important role in this event. In agreement, AML1-ETO overexpression in leukemic U937 cells activated c-Jun N-terminal kinase (JNK), while its specific inhibitor SP600125 effectively abrogated AML1-ETO-induced Cx43 expression, indicating that JNK signaling pathway contributes to AML1-ETO induced Cx43 expression. These results would shed new insights for understanding mechanisms of AML1-ETO-associated leukemogenesis.
AML1-ETO融合蛋白是白血病相关染色体易位t(8;21)的产物，据报道它可上调连接蛋白-43（Cx43）的表达，Cx43是构成间隙连接的连接蛋白家族的成员。然而，其机制仍不清楚。通过生物信息学分析，我们在此表明，在Cx43基因上游的5'-侧翼区域有两个假定的AML1结合共有序列，其后跟着两个活化蛋白（AP）1位点。在电泳迁移率变动分析中，AML1-ETO可直接结合这两个AML1结合位点，但荧光素酶报告基因分析显示，AML1结合位点对于AML1-ETO蛋白诱导Cx43表达并非必不可少。相反，AP1位点在此过程中发挥重要作用。与此一致的是，白血病U937细胞中AML1-ETO的过表达激活了c-Jun氨基末端激酶（JNK），而其特异性抑制剂SP600125有效消除了AML1-ETO诱导的Cx43表达，表明JNK信号通路有助于AML1-ETO诱导的Cx43表达。这些结果将为理解AML1-ETO相关白血病发生机制提供新的见解。
