Harrod R, Gu Z, Lovett P S
Department of Biological Sciences, University of Maryland Baltimore County, Catonsville 21228.
Gene. 1994 Mar 11;140(1):79-83. doi: 10.1016/0378-1119(94)90734-x.
Induction of chloramphenicol (Cm) acetyltransferase-encoding genes (cat) by Cm has been proposed to result from the destabilization of a stem-loop that sequesters the ribosome-binding site for the cat coding sequence. Destabilization is caused by the stalling of a ribosome at a specific site in the leader of cat transcripts that immediately precedes the stem-loop. By use of in vivo dimethylsulfate probing of cat-86 leader mRNA, we demonstrate the existence of the stem-loop structure in cat transcripts isolated from uninduced cells and its release during induction. Leader mutations chosen to provide the mRNA with an alternative folding pattern that destabilizes the stem-loop cause constitutive cat expression. Our results establish the occurrence in vivo of the stem-loop in cat-86 transcripts and its role as a negative regulator of cat expression.
有人提出，氯霉素（Cm）可诱导氯霉素乙酰转移酶编码基因（cat），这是由于一个茎环结构不稳定，该茎环结构隔离了cat编码序列的核糖体结合位点。核糖体在紧邻茎环的cat转录本前导序列中的特定位点停滞，从而导致该茎环结构不稳定。通过对cat-86前导mRNA进行体内硫酸二甲酯探测，我们证明了从未诱导细胞中分离出的cat转录本中存在茎环结构，并且在诱导过程中该结构会释放。选择的前导突变可使mRNA形成一种使茎环结构不稳定的替代折叠模式，从而导致cat组成型表达。我们的结果证实了cat-86转录本中茎环结构在体内的存在及其作为cat表达负调控因子的作用。
