Hwang A, Maity A, McKenna W G, Muschel R J
Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia 19104, USA.
J Biol Chem. 1995 Nov 24;270(47):28419-24. doi: 10.1074/jbc.270.47.28419.
Cyclin B1 mRNA expression varies through the cell cycle with its peak in G2/M. In cycling mammalian cells, its lowest level is in G1 with a steady increase in S until a level 50-fold greater than that in G1 is reached. In order to characterize the transcriptional component to this variation in expression, we cloned the upstream region 872 base pairs upstream from the start site of the cyclin B1 gene and have demonstrated that it confers cell cycle-dependent regulation onto two reporter genes, both chloramphenicol acetyltransferase and luciferase. Its activity was 25-fold greater in G2/M than in G1 in HeLa cells with intermediate activity in S. This cyclical activity could be seen with sequences encompassing only 90 base pairs upstream from the start site. Protein binding to this region was demonstrated using electrophoretic mobility shift assays, and the binding profiles appeared to vary depending upon the phase of the cycle in which the extracts are made. Thus, transcriptional control plays an important role in determining cyclin B1 mRNA levels, and cell cycle-dependent activity is regulated through interactions with the region 90 bases upstream from the start site.
细胞周期蛋白B1（Cyclin B1）的信使核糖核酸（mRNA）表达在整个细胞周期中有所变化，在G2/M期达到峰值。在处于细胞周期的哺乳动物细胞中，其最低水平出现在G1期，在S期稳步上升，直至达到比G1期高50倍的水平。为了描述这种表达变化的转录成分，我们克隆了细胞周期蛋白B1基因起始位点上游872个碱基对的上游区域，并证明它能赋予氯霉素乙酰转移酶和荧光素酶这两个报告基因细胞周期依赖性调控。在HeLa细胞中，其在G2/M期的活性比在G1期高25倍，在S期活性处于中间水平。仅用起始位点上游90个碱基对的序列就能观察到这种周期性活性。用电泳迁移率变动分析证明了蛋白质与该区域的结合，且结合图谱似乎因制备提取物时细胞所处的周期阶段而异。因此，转录控制在决定细胞周期蛋白B1的mRNA水平方面起着重要作用，且细胞周期依赖性活性是通过与起始位点上游90个碱基的区域相互作用来调控的。
