Voulgari Angeliki, Voskou Stella, Tora Làszlò, Davidson Irwin, Sasazuki Takehiko, Shirasawa Senji, Pintzas Alexander
Laboratory of Signal Mediated Gene Expression, Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, 48 Vasileos Konstantinou Avenue, Athens 11635, Greece.
Mol Cancer Res. 2008 Jun;6(6):1071-83. doi: 10.1158/1541-7786.MCR-07-0375.
Activating mutations in the RAS proto-oncogene result in constant stimulation of its downstream pathways, further leading to tumorigenesis. Transcription factor IID (TFIID) can be regulated by cellular signals to specifically alter transcription of particular subsets of genes. To investigate potential links between the regulation of TFIID function and the RAS-induced carcinogenesis, we monitored the expression of the TATA box-binding protein and its associated factors (TAF) in human colon carcinoma cells. We primarily identified TAF12 levels as being up-regulated in cell lines bearing natural RAS mutations or stably overexpressing a mutated RAS isoform via a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-dependent pathway. We further showed by electrophoretic mobility shift assays and chromatin immunoprecipitation that the ETS1 protein was interacting with an ETS-binding site on the TAF12 promoter and was regulating TAF12 expression. The binding was enhanced in extracts from oncogenic RAS-transformed cells, pointing to a role in the RAS-mediated regulation of TAF12 expression. Reduction of TAF12 levels by small interfering RNA treatment induced a destabilization of the TFIID complex, enhanced E-cadherin mRNA and protein levels, and reduced migration and adhesion properties of RAS-transformed cells with epithelial to mesenchymal transition. Overall, our study indicates the importance of TAF12 in the process of RAS-induced transformation properties of human colon cells and epithelial to mesenchymal transition, most notably those related to increased motility, by regulating specifically expression of genes such as E-cadherin.
RAS原癌基因中的激活突变导致其下游通路持续受到刺激，进而引发肿瘤发生。转录因子IID（TFIID）可受细胞信号调控，从而特异性改变特定基因子集的转录。为了研究TFIID功能调控与RAS诱导的致癌作用之间的潜在联系，我们监测了人结肠癌细胞中TATA盒结合蛋白及其相关因子（TAF）的表达。我们主要发现，在携带天然RAS突变或通过丝裂原活化蛋白激酶/细胞外信号调节激酶激酶依赖性途径稳定过表达突变RAS异构体的细胞系中，TAF12水平上调。我们通过电泳迁移率变动分析和染色质免疫沉淀进一步表明，ETS1蛋白与TAF12启动子上的ETS结合位点相互作用，并调节TAF12的表达。在致癌RAS转化细胞的提取物中，这种结合增强，表明其在RAS介导的TAF12表达调控中发挥作用。通过小干扰RNA处理降低TAF12水平，会导致TFIID复合物不稳定，增强E-钙黏蛋白mRNA和蛋白水平，并降低RAS转化细胞发生上皮-间质转化后的迁移和黏附特性。总体而言，我们的研究表明，TAF12在RAS诱导的人结肠细胞转化特性及上皮-间质转化过程中具有重要作用，最显著的是通过特异性调节E-钙黏蛋白等基因的表达，与增加的运动性相关。
