Zhou Y N, Jin D J
Laboratory of Molecular Biology, Building 37, Room 2E14, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):2908-13. doi: 10.1073/pnas.95.6.2908.
In Escherichia coli, stringently controlled genes are highly transcribed during rapid growth, but "turned off" under nutrient limiting conditions, a process called the stringent response. To understand how transcriptional initiation at these promoters is coordinately regulated, we analyzed the interactions between RNA polymerase (RNAP) (both wild type and mutants) and four stringently controlled promoters. Our results show that the interactions between RNAP and stringently controlled promoters are intrinsically unstable and can alternate between relatively stable and metastable states. The mutant RNAPs appear to specifically further weaken interactions with these promoters in vitro and behave like "stringent" RNAPs in the absence of the stringent response in vivo, constituting a novel class of mutant RNAPs. Consistently, these mutant RNAPs also activate the expression of other genes that normally require the response. We propose that the stability of initiation complexes is coupled to the transcription of stringently controlled promoters, and this unique feature coordinates the expression of genes positively and negatively regulated by the stringent response.
在大肠杆菌中，严格调控的基因在快速生长期间高度转录，但在营养限制条件下“关闭”，这一过程称为严格反应。为了了解这些启动子处的转录起始是如何协同调控的，我们分析了RNA聚合酶（RNAP）（野生型和突变体）与四个严格调控的启动子之间的相互作用。我们的结果表明，RNAP与严格调控的启动子之间的相互作用本质上是不稳定的，并且可以在相对稳定和亚稳定状态之间交替。突变型RNAP在体外似乎会特别进一步削弱与这些启动子的相互作用，并且在体内不存在严格反应的情况下表现得像“严格”的RNAP，构成了一类新型的突变型RNAP。一致地，这些突变型RNAP还激活了其他通常需要该反应的基因的表达。我们提出，起始复合物的稳定性与严格调控的启动子的转录相关联，并且这一独特特征协调了受严格反应正向和负向调控的基因的表达。
