Cannon W V, Gallegos M T, Buck M
Department of Biology, Sir Alexander Fleming Building, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK.
Nat Struct Biol. 2000 Jul;7(7):594-601. doi: 10.1038/76830.
Multisubunit RNA polymerases are targets of sophisticated signal transduction pathways that link environmental or temporal cues to changes in gene expression. Here we show that the sigma 54 protein (sigma54), responsible for promoter specific binding by bacterial RNA polymerase, undergoes a nucleotide hydrolysis dependent isomerization on DNA. Changes in protein structure are evident. The isomerization has all the known requirements of sigma 54-dependent transcription, including a dependence on enhancer binding activator proteins and occurs independently of the core RNA polymerase. We suggest that activator driven changes in sigma54 conformation trigger the conversion of a transcriptionally silent RNA polymerase conformation to one able to interact productively with template DNA. Our results illustrate the types of changes that must occur for multisubunit complexes to manipulate DNA, and show that transcription activators can remodel key nucleoprotein structures to achieve direct activation of transcription.
多亚基RNA聚合酶是复杂信号转导途径的靶点，这些途径将环境或时间线索与基因表达的变化联系起来。在这里，我们表明负责细菌RNA聚合酶启动子特异性结合的σ54蛋白（sigma54）在DNA上经历了核苷酸水解依赖性异构化。蛋白质结构的变化很明显。这种异构化具有σ54依赖性转录的所有已知要求，包括对增强子结合激活蛋白的依赖性，并且独立于核心RNA聚合酶发生。我们认为激活剂驱动的sigma54构象变化触发了转录沉默的RNA聚合酶构象向能够与模板DNA有效相互作用的构象的转变。我们的结果说明了多亚基复合物操纵DNA时必须发生的变化类型，并表明转录激活剂可以重塑关键的核蛋白结构以实现转录的直接激活。
