Hernández-Arranz Sofía, Sánchez-Hevia Dione, Rojo Fernando, Moreno Renata
Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Cantoblanco, 28049 Madrid, Spain.
RNA. 2016 Dec;22(12):1902-1917. doi: 10.1261/rna.058313.116. Epub 2016 Oct 24.
In Pseudomonas putida, the Hfq and Crc proteins regulate the expression of many genes in response to nutritional and environmental cues, by binding to mRNAs that bear specific target motifs and inhibiting their translation. The effect of these two proteins is antagonized by the CrcZ and CrcY small RNAs (sRNAs), the levels of which vary greatly according to growth conditions. The crcZ and crcY genes are transcribed from promoters PcrcZ and PcrcY, respectively, a process that relies on the CbrB transcriptional activator and the RpoN σ factor. Here we show that crcZ can also be transcribed from the promoter of the immediate upstream gene, cbrB, a weak constitutive promoter. The cbrB-crcZ transcript was processed to render a sRNA very similar in size to the CrcZ produced from promoter PcrcZ The processed sRNA, termed CrcZ*, was able to antagonize Hfq/Crc because, when provided in trans, it relieved the deregulated Hfq/Crc-dependent hyperrepressing phenotype of a ΔcrcZΔcrcY strain. CrcZ* may help in attaining basal levels of CrcZ/CrcZ* that are sufficient to protect the cell from an excessive Hfq/Crc-dependent repression. Since a functional sRNA can be produced from PcrcZ, an inducible strong promoter, or by cleavage of the cbrB-crcZ mRNA, crcZ can be considered a 3'-untranslated region of the cbrB-crcZ mRNA. In the absence of Hfq, the processed form of CrcZ was not observed. In addition, we show that Crc and Hfq increase CrcZ stability, which supports the idea that these proteins can form a complex with CrcZ and protect it from degradation by RNases.
在恶臭假单胞菌中，Hfq和Crc蛋白通过与带有特定靶基序的mRNA结合并抑制其翻译，响应营养和环境信号来调节许多基因的表达。这两种蛋白的作用被CrcZ和CrcY小RNA（sRNA）拮抗，它们的水平根据生长条件有很大差异。crcZ和crcY基因分别从启动子PcrcZ和PcrcY转录，这一过程依赖于CbrB转录激活因子和RpoN σ因子。在这里，我们表明crcZ也可以从紧邻的上游基因cbrB的启动子转录，cbrB是一个弱组成型启动子。cbrB - crcZ转录本经过加工后产生一种大小与从启动子PcrcZ产生的CrcZ非常相似的sRNA。加工后的sRNA称为CrcZ*，它能够拮抗Hfq/Crc，因为当反式提供时，它缓解了ΔcrcZΔcrcY菌株中失调的Hfq/Crc依赖性过度抑制表型。CrcZ可能有助于达到足以保护细胞免受过度的Hfq/Crc依赖性抑制的CrcZ/CrcZ基础水平。由于功能性sRNA可以从诱导型强启动子PcrcZ产生，或者通过cbrB - crcZ mRNA的切割产生，crcZ可以被认为是cbrB - crcZ mRNA的3'非翻译区。在没有Hfq的情况下，未观察到CrcZ的加工形式。此外，我们表明Crc和Hfq增加了CrcZ的稳定性，这支持了这些蛋白可以与CrcZ形成复合物并保护其免受核糖核酸酶降解的观点。
