Mishra R K, Gopal V, Chatterji D
Centre for Cellular and Molecular Biology, Hyderabad, India.
FEBS Lett. 1990 Jan 29;260(2):273-6. doi: 10.1016/0014-5793(90)80121-x.
Binding of Escherichia coli RNA polymerase and the abortive initiation of transcription at the A2 promoter of bacteriophage T7, separately cloned in pBR322, was found to be strongly dependent on the degree of supercoiling of the plasmid. Supercoiling does not seem to play any role in the initiation of transcription at the T7A1 promoter under identical conditions. Plasmid containing T7A2 promoter was found to be less amenable to S1 nuclease in comparison to that having T7A1. Sequence comparison reveals a high G/C content upstream to the -35 region of T7A2 which by extra duplex stability probably renders the initiation of transcription more dependent on the state of supercoiling of the template.
分别克隆于pBR322中的大肠杆菌RNA聚合酶与噬菌体T7 A2启动子处转录的流产起始的结合，被发现强烈依赖于质粒的超螺旋程度。在相同条件下，超螺旋似乎在T7A1启动子的转录起始中不发挥任何作用。与含有T7A1的质粒相比，含有T7A2启动子的质粒对S1核酸酶的敏感性较低。序列比较显示，T7A2的-35区域上游具有高G/C含量，这可能通过额外的双链稳定性使转录起始更依赖于模板的超螺旋状态。
