Zhao X Y, Hung M C
Department of Tumor Biology, University of Texas M. D. Anderson Cancer Center, Houston 77030.
Mol Cell Biol. 1992 Jun;12(6):2739-48. doi: 10.1128/mcb.12.6.2739-2748.1992.
In an attempt to study potential feedback regulation of the neu oncogene, we have found that the neu oncogene product specifically represses its own promoter activity. Deletion analysis indicated a 140-bp region (nucleotides -312 to -173 relative to the ATG initiation codon) in the rat neu promoter responsible for neu autorepression. Gel shift assays and methylation interference analysis further demonstrated that a GGTGGGGGGG sequence (nucleotides -243 to -234 relative to the ATG initiation codon) in this 140-bp region interacts with specific protein complexes. The GGTGGGGGGG sequence (GTG element), which functions as an enhancer, is sufficient to cause neu-mediated repression in a heterologous promoter. Furthermore, it produces different gel shift patterns with nuclear extracts from neu-transformed cell lines and their parental lines, suggesting that a transcriptional factor(s) interacting with this enhancer element has been perturbed by the introduction of neu. Taken together, the data presented in this report show that (i) the neu oncogene product autorepresses its own promoter, (ii) the neu promoter contains a novel enhancer, and (iii) neu autorepression is mediated through this enhancer, likely by inhibition of the enhancer activity.
为了研究neu癌基因的潜在反馈调节，我们发现neu癌基因产物特异性地抑制其自身的启动子活性。缺失分析表明，大鼠neu启动子中有一个140bp的区域（相对于ATG起始密码子为核苷酸-312至-173）负责neu的自我抑制。凝胶迁移实验和甲基化干扰分析进一步证明，该140bp区域中的一个GGTGGGGGGG序列（相对于ATG起始密码子为核苷酸-243至-234）与特定的蛋白质复合物相互作用。作为增强子发挥作用的GGTGGGGGGG序列（GTG元件）足以在异源启动子中引起neu介导的抑制。此外，它与neu转化细胞系及其亲代细胞系的核提取物产生不同的凝胶迁移模式，表明与该增强子元件相互作用的一种或多种转录因子已因neu的引入而受到干扰。综上所述，本报告中的数据表明：（i）neu癌基因产物自我抑制其自身启动子；（ii）neu启动子包含一个新的增强子；（iii）neu自我抑制是通过该增强子介导的，可能是通过抑制增强子活性实现的。
