Functional analysis of the RNA polymerase binding protein RbpA in Streptomyces coelicolor

在所有生物体中，基因的开启或关闭都是对环境、发育或生理线索的反应。在细菌中，控制基因表达的关键步骤是转录起始。转录起始通过几个步骤进行，包括“RNA聚合酶”复合物与基因上游的“启动子”序列结合，打开双链DNA以暴露单链模板，以及在模板链上合成信使RNA（mRNA）（mRNA随后在蛋白质的产生中由核糖体解码）。转录起始的频率由调节蛋白控制，其中大多数与启动子区的DNA结合，通常也与RNA聚合酶相互作用。此外，几种蛋白质与RNA聚合酶稳定地相互作用以调节其活性而不与DNA结合。RbpA是工业上重要的产毒细菌天蓝色链霉菌中的RNA聚合酶结合蛋白。这种微生物是一个大家族细菌的典型代表，这些细菌产生当今使用的大多数抗生素。我们的初步数据表明，RbpA通过激活这些蛋白质工厂的RNA组分的表达来调节核糖体的产生。在所有生物体中，核糖体的产生都受到蛋白质合成需求和营养可用性的非常仔细的调节，导致核糖体数量和生长速率之间的密切相关性。缺乏这种蛋白质的突变体生长缓慢的发现强调了RbpA的重要性。去除RbpA的另一个有趣的结果是对利福平的敏感性增加，利福平是一种结合RNA聚合酶并阻断转录起始的抗生素。该项目的总体目标是了解RbpA如何调节核糖体RNA合成。这项研究很重要，因为链霉菌细菌中抗生素的产生与生长速度有关：抗生素通常只在生物体停止复制时产生。RbpA相关蛋白质也存在于相关病原生物体中，包括结核分枝杆菌，其每年夺去约200万人的生命。利福平是用于对抗这种病原体的一线药物，尽管耐药突变体是一个日益严重的问题。因此，本研究的结果将与研究该生物体中利福平耐药的生长速率和机制的研究人员相关。

In all organisms genes are switched on or off in response to environmental, developmental or physiological cues. In bacteria, the key step in the control of gene expression is transcription initiation. Transcription initiation proceeds via several steps including the binding of an 'RNA polymerase' complex to a 'promoter' sequence upstream of the gene, opening of the double-stranded DNA to expose the single-stranded template, and synthesis of messenger RNA (mRNA) on the template strand (mRNA is subsequently decoded by ribosomes in the production of proteins). The frequency of transcription initiation is controlled by regulatory proteins, most of which bind to DNA in the promoter region, often also interacting with RNA polymerase. In addition, several proteins interact stably with RNA polymerase to modulate its activity without binding to DNA. RbpA is an RNA polymerase binding protein in the industrially important antibiotic-producing bacterium Streptomyces coelicolor. This organism is the model representative of a large family of bacteria that produce the majority of antibiotics in use today. Our preliminary data suggests that RbpA regulates the production of ribosomes, by activating expression of the RNA component of these protein factories. In all organisms ribosome production is very carefully regulated in response to protein synthesis needs and nutrient availability, leading to a close correlation between ribosome numbers and growth rate. The importance of RbpA is underlined by the finding that mutants that lack this protein grow slowly. Another interesting consequence of removing RbpA is increased sensitivity to rifampicin, an antibiotic that binds RNA polymerase and blocks transcription initiation. The overall aim of this project is to understand how RbpA regulates ribosomal RNA synthesis. This research is important because antibiotic production in the Streptomyces bacteria is linked to growth rate: antibiotics are usually only produced when the organism stops replicating. RbpA-related proteins are also found in related pathogenic organisms, including Mycobacterium tuberculosis, which claims ~2 million lives annually. Rifampicin is a front-line drug used to combat this pathogen, although drug-resistant mutants are an increasing problem. Therefore the outcomes of this research will be relevant to researchers investigating both growth rate and mechanisms of rifampicin resistance in this organism.