Harris L C, Remack J S, Brent T P
Department of Molecular Pharmacology, St Jude Children's Research Hospital, Memphis, TN 38101-0318.
Nucleic Acids Res. 1994 Nov 11;22(22):4614-9. doi: 10.1093/nar/22.22.4614.
The DNA repair enzyme, O6-methylguanine DNA methyltransferase (MGMT) is responsible for repair of damage induced by alkylating agents that produce adducts at O6-guanine in DNA. Although the MGMT gene promoter has housekeeping gene promoter characteristics, unlike these genes which are expressed at a constant level, MGMT transcriptional activity varies between cell types. During an attempt to identify regions of the MGMT regulatory sequence sensitive to variations in transcription factors between cell types, we have identified a 59 bp enhancer which is required for efficient MGMT promoter function. This fragment produced increased transcriptional activity in reporter gene constructs containing either the MGMT or UMP-synthase promoter when transfected into either of two cell lines; it seems therefore that this enhancer may interact with relatively common trans-acting factors. Functional activity is only detected when the enhancer is in 'cis' with respect to the promoter, suggesting that complexes are formed between proteins bound to the enhancer and promoter sequences. We propose that the enhancer-binding protein may be a novel transcription factor since there are no obvious consensus sequences within the 59 bp sequence for known DNA-binding proteins.
DNA修复酶O6-甲基鸟嘌呤DNA甲基转移酶（MGMT）负责修复由在DNA的O6-鸟嘌呤处产生加合物的烷化剂所诱导的损伤。尽管MGMT基因启动子具有管家基因启动子的特征，但与那些以恒定水平表达的基因不同，MGMT的转录活性在不同细胞类型之间存在差异。在试图鉴定MGMT调控序列中对不同细胞类型间转录因子变化敏感的区域时，我们鉴定出了一个59 bp的增强子，它是MGMT启动子有效发挥功能所必需的。当将该片段转染到两种细胞系中的任何一种时，它在含有MGMT或尿苷酸合酶启动子的报告基因构建体中产生了增强的转录活性；因此，这个增强子似乎可能与相对常见的反式作用因子相互作用。只有当增强子与启动子处于“顺式”时才能检测到功能活性，这表明在结合于增强子和启动子序列的蛋白质之间形成了复合物。我们提出，增强子结合蛋白可能是一种新型转录因子，因为在这59 bp序列中没有已知DNA结合蛋白的明显共有序列。
