2014.07.19【英译中】SCI 连载之四

小妮丫头 (流火) 路人甲
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发表于:2014-07-19 21:31 [只看楼主] [划词开启]

2014.07.19【英译中】SCI 连载之四


Ribosome engineering

核糖体工程

Ribosome engineering is effective for activation of silent genes. For example, among the 1,068 actinomycetes isolated from soil, a fraction of the Streptomyces isolates and most of the non-Streptomyces isolates were found to be nonproducers of antibiotics, with 43 and 6 %, respectively, of these nonproducing strains acquiring the ability to synthesize antibacterials against Staphylococcus aureus after a selection step that generated spontaneous rpsL or rpoB mutations (Hosaka et al. 2009). Assessment of Streptomyces mauvecolor 631689, a strain that produced no antibacterial activity in any medium tested, demonstrated that two rpoB mutants (H437D or H437L), a double mutant of rpoB(H437L) and rpsL (K88R), and a gentamicin-resistant (GenR) mutant produced a family of antibiotics, the piperidamycins (Fig.1). The activation of silent genes by the rpoB H437D or H437L mutations was attributed, at least in part, to the increased affinity of mutant RNAP for the silent gene promoters (Hosaka et al.2009).

核糖体工程在激活沉默基因方面很有成效。比如说,从土壤中分离的1068中放线菌,链霉菌属中的部分分离物和大部分的非链霉菌属分离物被认为没有抗生素产生,其百分比约占43%6%。这些不会产生抗生素的菌株在经过筛选后自发产生了rpsL 或者 rpoB基因突变,获得了合成抗菌药物抗金黄色葡萄球菌的能力。Streptomyces mauvecolor 631689原本在任何测试培养基中均显示没有抑菌活性,但对其评估研究显示,它的两株rpoB H437D 或者 H437L)突变体、rpoB(H437L) rpsL (K88R)双位点突变体以及庆大抗性突变体能够产生一系列抗生素——piperidamycin系列。沉默基因rpoB H437D 或者 H437L位点的激活主要(至少有一部分原因)是因为RNAP突变体对沉默基因的启动子亲和力增强。

 

Species of Bacillus produce a variety of commercially important metabolites and extracellular enzymes. The introduction of the rpoB mutation S487L into a Bacillus subtilis strain resulted in cells that overproduced an aminosugar antibiotic, 3,3-neotrehalosadiamine (NTD), the production of which is dormant in the wild-type strain (Inaoka et al.2004). Perhaps, unlike the wild-type RNAP, the mutant RNAP efficiently recognized the σ A -dependent promoters, resulting in the dramatic activation of the NTD biosynthesis pathway. Although most of the work was performed using S. lividans, we have now demonstrated that rpoB mutations are widely effective in activating silent and poorly expressed secondary metabolite-biosynthetic gene clusters at the transcriptional level in Streptomyces griseus (up to 70-fold activation), S. coelicolor (up to eightfold activation), and S. erythraea (up to sevenfold activation; Tanaka and Ochi, manuscript in preparation). Notably, the activation of silent gene clusters by rpoB mutations was medium-dependent, with each rpoB mutation exerting differential effects on the activation of each silent gene cluster. These findings suggest that strains containing rpoB mutations (e.g., H437Y, H437R) should be grown in different media to assess the full spectrum of silent gene activation.

芽孢杆菌属的一些种产生多种商业重要的次级代谢产物和胞外酶。rpoB基因的S487L型突变体导入到枯草芽孢杆菌菌株当中,能够使细胞过量表达氨基糖类抗生素——NTD,正常情况下的野生型菌株是不产生这种物质的。可能,与野生型RNAP不同,突变型RNAP能够有效识别σ A 依赖型启动子,最终十分引人注目的激发了NTD的合成途径。虽然大部分研究工作都在S. lividans中进行,现在我们已经证明,rpoB突变体能够广泛用于转录水平上来激活沉默基因和弱表达的次级代谢生物合成基因簇,如在Streptomyces griseus70倍之多,S. coelicolor中激活了8倍,S. erythraea中有7倍。值得注意的是,rpoB突变体沉默基因簇的激活是需要依赖培养基的,每个rpoB突变体在不同沉默基因簇的激活上产生不同的作用和影响。这些发现提示我们,含不同rpoB基因突变子的菌株需要在不同的培养基上生长,并以此来完全评估沉默基因激活的程度。

分类: 英语

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