Allan M, Zhu J D, Montague P, Paul J
Cell. 1984 Sep;38(2):399-407. doi: 10.1016/0092-8674(84)90495-1.
The human epsilon-globin gene has a number of alternative transcription-initiation sites located upstream of the canonical mRNA cap site. In three nonerythroid cell lines, "leaky" epsilon-globin transcription occurs exclusively from one of these upstream sites, the -200 cap site. Using a transient expression assay, we have shown that transcription initiation from the -200 cap site and the major cap site can be independently regulated in response to plasmid replication, SV40 enhancer sequences in cis, and the adenovirus E1A gene in trans. The -200 cap site is located within a region of S1 hypersensitivity in the supercoiled plasmid, and in the absence of viral enhancer sequences it is the main initiation site following transfection into a number of cell lines. We suggest that the -200 cap site acts as a polymerase entry site by virtue of its accessible chromatin structure. The efficiency of polymerase binding at this site may be altered by trans-acting regulatory molecules.
人类ε-珠蛋白基因在典型mRNA帽位点上游有多个可变转录起始位点。在三种非红细胞系中，“渗漏性”ε-珠蛋白转录仅从这些上游位点之一，即-200帽位点发生。通过瞬时表达分析，我们已经表明，来自-200帽位点和主要帽位点的转录起始可以响应质粒复制、顺式的SV40增强子序列以及反式的腺病毒E1A基因而独立调节。-200帽位点位于超螺旋质粒中S1超敏区域内，并且在没有病毒增强子序列的情况下，它是转染到许多细胞系后的主要起始位点。我们认为，-200帽位点凭借其可及的染色质结构充当聚合酶进入位点。该位点处聚合酶结合的效率可能会被反式作用调节分子改变。
