Promoter recognition by Bacillus subtilis σW:: Autoregulation and partial overlap with the σX regulon
Promoter recognition by Bacillus subtilis σW:: Autoregulation and partial overlap with the σX regulon
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DOI：
10.1128/jb.180.15.3765-3770.1998
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发表时间：
1998-08-01
影响因子：
3.2
通讯作者：
Helmann, JD
中科院分区：
文献类型：
--
作者：
Huang, XJ;Fredrick, KL;Helmann, JD
枯草芽孢杆菌基因组编码至少17种不同的σ因子，包括细胞质外功能（ECF）亚家族的7个成员。我们研究了由sigW基因编码的ECF α因子的表达和调节。sigma（W）依赖性启动子（P-W）位于sigW之前，表明该转录因子是正性自动调节的。sigW的表达受生长期和培养基组成的调节。在生长于丰富培养基中的早期稳定期细胞中获得最大表达。我们以前报道过sigW突变体提高了一些sigma（X）控制基因的转录，我们现在报道匡威也是如此：在sigX突变体中，P-W在对数生长期间被去抑制。因此，这两种调节子是相互对立的。重构的sigma（W）全酶忠实地识别sigW之前的P-W，但不识别sigX基因之前的P-X启动子。sigX的自动调节也是高度特异性的：sigma（X）全酶从P-X启动转录，但识别P-W很差，如果有的话。相比之下，至少部分地在σ（X）控制下的几种启动子在体外对σ（X）和σ（W）全酶都有活性。这一发现支持了sigma（W）和sigma（X）调节子重叠的建议。序列比较表明，这两个α因子识别的启动子具有相似的-35元件，但在-10元件内的两个关键位置上具有不同的碱基偏好。
The Bacillus subtilis genome encodes at least 17 distinct sigma factors, including seven members of the extracytoplasmic function (ECF) subfamily, We have investigated the expression and regulation of the ECF a factor encoded by the sigW gene. A sigma(W)-dependent promoter (P-W) precedes sigW, demonstrating that this transcription factor is positively autoregulated. Expression of sigW is regulated by both growth phase and medium composition. Maximal expression is attained in early-stationary-phase cells grown in rich medium. We previously reported that sigW mutants have elevated transcription of some sigma(X)-controlled genes, and we now report that the converse is also true: in a sigX mutant, P-W is derepressed during logarithmic growth. Thus, these two regulons are mutually antagonistic. Reconstituted sigma(W) holoenzyme faithfully recognizes the P-W preceding sigW but does not recognize the P-X promoter preceding the sigX gene. Autoregulation of sigX is also highly specific: sigma(X) holoenzyme initiates transcription from P-X but recognizes P-W poorly if at all. In contrast, several promoters that are at least partially under sigma(X) control are active with both the sigma(X) and sigma(W) holoenzymes in vitro. This finding supports the suggestion that the sigma(W) and sigma(X) regulons overlap. Sequence comparisons suggest that promoters recognized by these two a factors have similar -35 elements but are distinguished by different base preferences at two key positions within the -10 element.