Treisman R, Green M R, Maniatis T
Proc Natl Acad Sci U S A. 1983 Dec;80(24):7428-32. doi: 10.1073/pnas.80.24.7428.
We examined the effects of the simian virus 40 enhancer sequence on transcription of cloned human alpha- and beta-globin genes shortly after their introduction into cultured mammalian cells. We find that (i) detectable transcription of the beta-globin gene but not the alpha-globin gene requires linkage to the enhancer; (ii) the enhancer increases the amount of beta-globin RNA at least 100-fold but results in only a 5- to 10-fold increase in the amount of alpha-globin RNA; (iii) plasmid replication does not increase the level of beta-globin RNA, regardless of linkage to the enhancer, but does result in an approximately equal to 50-fold increase in the level of alpha-globin RNA; (iv) the enhancer is not required for and does not increase transcription of either gene in 293 cells, an adenovirus 5-transformed human kidney cell line. We also show that an enhancer sequence is not required for activity of the normally enhancer-dependent simian virus 40 early promoter in 293 cells, indicating that these cells contain a trans-acting factor(s) that circumvents the requirement for the enhancer sequence.
在将克隆的人α-和β-珠蛋白基因导入培养的哺乳动物细胞后不久，我们检测了猿猴病毒40增强子序列对其转录的影响。我们发现：（i）β-珠蛋白基因可检测到的转录，但α-珠蛋白基因则不然，这需要与增强子相连；（ii）增强子使β-珠蛋白RNA的量增加至少100倍，但α-珠蛋白RNA的量仅增加5至10倍；（iii）质粒复制不会增加β-珠蛋白RNA的水平，无论是否与增强子相连，但确实会使α-珠蛋白RNA的水平增加约50倍；（iv）在293细胞（一种腺病毒5转化的人肾细胞系）中，增强子对于这两个基因的转录既不是必需的，也不会增加其转录。我们还表明，在293细胞中，正常依赖增强子的猿猴病毒40早期启动子的活性不需要增强子序列，这表明这些细胞含有一种反式作用因子，可绕过对增强子序列的需求。
