Abrams J M, Schimke R T
Department of Biological Sciences, Stanford University, California 94305.
Mol Cell Biol. 1989 Feb;9(2):620-8. doi: 10.1128/mcb.9.2.620-628.1989.
We have constructed hybrid dihydrofolate reductase (DHFR) genes which are controlled by the sterol-responsive hamster 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase promoter. Stable transfection frequencies of these chimeric templates into a DHFR-deficient Chinese hamster cell line indicate that the HMG CoA reductase promoter fragment confers DHFR transformation irrespective of its orientation relative to a downstream murine DHFR cDNA. Sterol-regulated levels of DHFR RNA and protein are detected from hybrid genes which carry a properly oriented promoter fragment. Constructions which invert this HMG CoA reductase promoter, however, generate DHFR RNA levels which do not respond to sterols. In the context of these transfected fusion genes, we present evidence of divergent opposite-strand transcription initiating from the HMG CoA reductase 5' fragment. In contrast, the endogenous HMG CoA reductase promoter region shows no apparent evidence of such bidirectional activity.
我们构建了由固醇反应性仓鼠3-羟基-3-甲基戊二酰辅酶A（HMG CoA）还原酶启动子控制的杂交二氢叶酸还原酶（DHFR）基因。将这些嵌合模板稳定转染到缺乏DHFR的中国仓鼠细胞系中的频率表明，HMG CoA还原酶启动子片段赋予DHFR转化能力，而与其相对于下游小鼠DHFR cDNA的方向无关。从携带正确方向启动子片段的杂交基因中检测到固醇调节的DHFR RNA和蛋白质水平。然而，将该HMG CoA还原酶启动子倒置的构建体产生的DHFR RNA水平对固醇无反应。在这些转染的融合基因的背景下，我们提供了从HMG CoA还原酶5'片段起始的相反链发散转录的证据。相比之下，内源性HMG CoA还原酶启动子区域没有明显的这种双向活性的证据。
