Temporal and selective association of multiple sigma factors with RNA polymerase during sporulation in Bacillus subtilis
Temporal and selective association of multiple sigma factors with RNA polymerase during sporulation in Bacillus subtilis
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DOI：
10.1046/j.1365-2443.2000.00307.x
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发表时间：
2000-02-01
期刊：
影响因子：
2.1
通讯作者：
Fujita, M
中科院分区：
文献类型：
--
作者：
Fujita, M
背景资料：在枯草芽孢杆菌的孢子形成过程中，不对称分裂产生两个细胞，前孢子和母细胞，它们遵循不同的发育路径。在孢子形成过程中，基因激活的时间和空间的高度有序程序由主要的RNA聚合酶全酶（E sigma（A））和包含发育中的sigma因子sigma（H）、sigma（F）、sigma（E）、sigma（G）和sigma（K）的替代全酶形式控制，这些全酶形式在发育过程中相继出现。多个σ因子与核心RNA聚合酶的时间和选择性关联的控制机制尚不清楚。作为解决这些问题的第一步，本报告定量了孢子形成过程中孢子囊中存在的RNA聚合酶每个亚基的量，并在体外分析了每个σ亚基对核心RNA聚合酶的相对亲和力。使用定量免疫印迹分析，E σ（A），E σ（H），发现在适当时间点相对于RNA聚合酶总量的E σ（E）和E σ（K）分别为15%、1%、6%和2%。因此，预测核心RNA聚合酶过量。核心RNA聚合酶和sigma（A）的水平在从营养生长到孢子形成的过渡期间保持恒定，而孢子形成特异性sigma因子以sigma（H）、sigma（E）和sigma（K）的顺序相继出现。体外转录系统中sigma因子之间的竞争实验揭示了sigma（A）相对于sigma（H）和sigma（E）对于开放启动子复合物形成的优势。这些结果是不一致的想法，晚出现的西格玛因素可以取代较早出现的西格玛从核心enzyme.Conclusions：作为核心RNA聚合酶是过量的，结果表明，连续的西格玛因素可以结合到核心RNA聚合酶，而不必取代较早出现的西格玛因素。因此，孢子形成期间的基因表达程序可能不需要核心RNA聚合酶上的一个sigma因子被另一个sigma因子取代的机制。
Background: During sporulation in Bacillus subtilis, an asymmetric division produces two cells, a forespore and mother cell, with which follow different developmental paths. The highly ordered programme of temporal and spatial gene activation during sporulation is governed by the principal RNA polymerase holoenzyme (E sigma(A)) and alternative holoenzyme forms containing the developmental sigma factors sigma(H), sigma(F), sigma(E), sigma(G) and sigma(K), which appear successively during development. The control mechanism(s) of temporal and selective association of multiple sigma factors with core RNA polymerase is unclear. As a first step to addressing these issues, this report quantifies the amount of each subunit of RNA polymerase that is present in the sporangium during sporulation, and analyses in vitro the relative affinities of each sigma subunit for core RNA polymerase.Results: Using quantitative immunoblot analysis, the amounts of E sigma(A), E sigma(H), E sigma(E) and E sigma(K) in relation to the total amount of RNA polymerase at appropriate time-points were found to be 15%, 1%, 6% and 2%, respectively. Therefore, the core RNA polymerase is predicted to be in excess. The level of core RNA polymerase and sigma(A) remained constant during the transition from vegetative growth to sporulation, whereas the sporulation-specific sigma factors appeared successively, in the order sigma(H), sigma(E) and sigma(K). Competition experiments between sigma factors in an in vitro transcription system revealed the dominance of sigma(A) over sigma(H) and sigma(E) for open promoter complex formation. These results are inconsistent with the idea that late appearing sigma factors can displace earlier appearing sigmas from the core enzyme.Conclusions: As the core RNA polymerase is in excess, the results suggest that successive sigma factors can bind to core RNA polymerase without having to displace earlier appearing sigma factors. Thus, the programme of gene expression during sporulation might not require mechanisms for the substitution of one sigma factor by another on the core RNA polymerase.