ИСТИНА

6S RNAs are widespread among all bacterial species and act as global inhibitors of transcription targeting RNA polymerase (RNAP). Direct interaction of 6S RNA with RNAP active site and further blocking of enzyme activity are provided by conservative secondary structure of the 6S RNA molecule, which mimics open conformation of DNA promoter. It is considered that 6S RNAs pause transcription and store housekeeping RNAP under unfavorable or stress conditions, thus preventing overconsumption of nutrients and prolonging cell life. The aim of the present research was to investigate the influence of 6S RNAs from Escherichia coli and Bacillus subtilis on cell viability and gene expression under extreme growth conditions including basic, acidic, osmotic and oxidative stresses. For this purpose mutant E. coli and B. subtilis cell lines with deletions of 6S RNA genes were cultivated in parallel with wild type strains. Changes of 6S RNAs expression profiles during different stages of cell growth were analyzed by Northern blotting. Effects of 6S RNA knockouts in B. subtilis on cell growth were negligible although this bacterium encodes two different 6S RNAs expressing mostly in exponential (6S 2) as well as in stationary (6S-1) phase . The most prominent phenotype was observed for 6S RNA-depleted E. coli strain in presence of H2O2. To elucidate putative proteins, which expression is regulated by this 6S RNA under oxidative stress, comparative proteomic analyses of mutant strains related to wild type cells was performed. Total protein extracts isolated from each strain were labeled by fluorescent dyes Cy5 and Cy2 and analyzed simultaneously by 2D gel electrophoresis. A set of different proteins affected by 6S RNA was identified finally by MALDI-spectrometry.