Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore - 560012, India.
Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore - 560064, India.
Microbiology (Reading). 2010 Jul;156(Pt 7):1942-1952. doi: 10.1099/mic.0.038620-0. Epub 2010 Mar 18.
DNA-protein interactions that occur during transcription initiation play an important role in regulating gene expression. To initiate transcription, RNA polymerase (RNAP) binds to promoters in a sequence-specific fashion. This is followed by a series of steps governed by the equilibrium binding and kinetic rate constants, which in turn determine the overall efficiency of the transcription process. We present here the first detailed kinetic analysis of promoter-RNAP interactions during transcription initiation in the sigma(A)-dependent promoters P(rrnAPCL1), P(rrnB) and P(gyr) of Mycobacterium smegmatis. The promoters show comparable equilibrium binding affinity but differ significantly in open complex formation, kinetics of isomerization and promoter clearance. Furthermore, the two rrn promoters exhibit varied kinetic properties during transcription initiation and appear to be subjected to different modes of regulation. In addition to distinct kinetic patterns, each one of the housekeeping promoters studied has its own rate-limiting step in the initiation pathway, indicating the differences in their regulation.
DNA-蛋白质相互作用发生在转录起始过程中，在调节基因表达方面起着重要作用。为了起始转录，RNA 聚合酶（RNAP）以序列特异性的方式结合到启动子上。随后，一系列步骤由平衡结合和动力学速率常数控制，这反过来又决定了转录过程的整体效率。我们在这里首次详细分析了分枝杆菌σ（A）依赖性启动子 P（rrnAPCL1）、P（rrnB）和 P（gyr）中启动子-RNAP 相互作用在转录起始过程中的动力学。这些启动子具有可比的平衡结合亲和力，但在开放复合物形成、异构化动力学和启动子清除方面存在显著差异。此外，这两个 rrn 启动子在转录起始过程中表现出不同的动力学特性，似乎受到不同的调控模式的影响。除了不同的动力学模式外，所研究的每个管家启动子在起始途径中都有其自己的限速步骤，这表明它们的调控存在差异。
