Functions of the σ<SUP>54</SUP> region I <i>in</i> <i>Trans</i> and implications for transcription activation

作     者：Gallegos, MT Cannon, WV Buck, M 

作者机构：Univ London Imperial Coll Sci Technol & Med Dept Biol London SW7 2AZ England 

出 版 物：《JOURNAL OF BIOLOGICAL CHEMISTRY》 (生物化学杂志)

年 卷 期：1999年第274卷第36期

页      面：25285-25290页

核心收录：

学科分类：0710[理学-生物学] 071010[理学-生物化学与分子生物学] 07[理学] 

主　　题：细菌蛋白质类/遗传学 细菌蛋白质类/代谢 DNA结合蛋白质类 指导DNA的RNA聚合酶类/遗传学 指导DNA的RNA聚合酶类/代谢 大肠杆菌/遗传学 大肠杆菌/代谢 大肠杆菌蛋白质类 基因表达调控 细菌 RNA聚合酶∑54 ∑因子/遗传学 ∑因子/代谢 转录 遗传 转录激活 

摘      要：Control of transcription frequently involves the direct interaction of activators with RNA polymerase, In bacteria, the formation of stable open promoter complexes by the sigma(54) RNA polymerase is critically dependent on sigma(54) amino Region I sequences. Their presence correlates with activator dependence, and removal allows the holoenzyme to engage productively with melted DNA independently of the activator. Using purified Region I sequences and holoenzymes containing full-length or Region I-deleted sigma(54), we have explored the involvement of Region I in transcription activation, Results show that Region I in trans inhibits a reversible conformational change in the holoenzyme believed to be polymerase isomerization. Evidence is presented indicating that the holoenzyme land not the promoter DNA per se) is one interacting target used by Region I in preventing polymerase isomerization, Activator overcomes this inhibition in a reaction requiring nucleotide hydrolysis. Region I in trans is able to inhibit activated transcription by the holoenzyme containing full-length sigma(54). Inhibition appeared to be noncompetitive with respect to the activator, suggesting that a direct activator interaction occurs with parts of the holoenzyme outside Region I. Stabilization of isomerized holoenzyme bound to melted DNA by Region I in trans occurs largely independently of the initiating nucleotide, suggesting a role for Region I in maintaining the open complex.