Rojo F, Nuez B, Mencía M, Salas M
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain.
Nucleic Acids Res. 1993 Feb 25;21(4):935-40. doi: 10.1093/nar/21.4.935.
Most Escherichia coli promoters studied so far form stable open complexes with sigma 70-RNA polymerase which have relatively long half-lives and, therefore, are resistant to a competitor challenge. A few exceptions are nevertheless known. The analysis of a number of promoters in Bacillus subtilis has suggested that the instability of open complexes formed by the vegetative sigma A-RNA polymerase may be a more general phenomenon than in Escherichia coli. We show that the main early and late promoters from the Bacillus subtilis phage phi 29 form unstable open complexes that are stabilized either by the formation of the first phosphodiester bond between the initiating nucleoside triphosphates or by DNA supercoiling. The functional characteristics of these two strong promoters suggest that they are not optimized for a tight and stable RNA polymerase binding. Their high activity is probably the consequence of the efficiency of further steps leading to the formation of an elongation complex.
到目前为止，大多数已研究的大肠杆菌启动子与σ⁷⁰-RNA聚合酶形成稳定的开放复合物，这些复合物具有相对较长的半衰期，因此对竞争挑战具有抗性。然而，也有一些例外情况是已知的。对枯草芽孢杆菌中多个启动子的分析表明，营养型σA-RNA聚合酶形成的开放复合物的不稳定性可能是比大肠杆菌中更普遍的现象。我们发现，枯草芽孢杆菌噬菌体φ29的主要早期和晚期启动子形成不稳定的开放复合物，这些复合物可通过起始核苷三磷酸之间形成第一个磷酸二酯键或通过DNA超螺旋而稳定。这两个强启动子的功能特性表明，它们并非为紧密且稳定的RNA聚合酶结合而优化。它们的高活性可能是导致延伸复合物形成的后续步骤效率的结果。
