M. tuberculosis transcriptional profile of delta pepD strain vs wild-type strain
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ABSTRACT:
ORGANISM(S): Mycobacterium tuberculosis
PROVIDER: GSE17587 | GEO | 2009/10/30
SECONDARY ACCESSION(S): PRJNA118519
REPOSITORIES: GEO
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Project description:pepD is regulated by a 2CS, MprAB, and impacts upon the regulation of sigE, an important M.tb sigma factor. Here we examine the global impact of gene regulation in a delta pepD mutant strain. Analysis compares total RNA from early log growth cultures of both wild-type and a delta pepD strain.
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Project description:pepD is regulated by a 2CS, MprAB, and impacts upon the regulation of sigE, an important M.tb sigma factor. Here we examine the global impact of gene regulation in a delta pepD mutant strain. Analysis compares total RNA from early log growth cultures of both wild-type and a delta pepD strain.
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Project description:The extracytoplasmic factor (ECF) sigma factor sigma(E) is one of the most studied sigma factors of Mycobacterium tuberculosis. It has been shown to be involved in virulence as well as in survival under conditions of high temperature, alkaline pH, and exposure to detergents and oxidative stress. Unlike many ECF sigma factors, sigma(E) does not directly regulate the transcription of its own gene. Two promoters have been identified upstream of the sigE gene; one is regulated by the two-component system MprAB, while the other has been shown to be sigma(H) dependent. In this paper, we further characterize the regulation of sigma(E) by identifying its anti-sigma factor and a previously unknown promoter. Finally, we show that sigE can be translated from three different translational start codons, depending on the promoter used. Taken together, our data demonstrate that sigma(E) not only is subjected to complex transcriptional regulation but is also controlled at the translational and posttranslational levels.
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Project description:Three new Anabaena sp. strain PCC 7120 genes encoding group 2 alternative sigma factors have been cloned and characterized. Insertional inactivation of sigD, sigE, and sigF genes did not affect growth on nitrate under standard laboratory conditions but did transiently impair the abilities of sigD and sigE mutant strains to establish diazotrophic growth. A sigD sigE double mutant, though proficient in growth on nitrate and still able to differentiate into distinct proheterocysts, was unable to grow diazotrophically due to extensive fragmentation of filaments upon nitrogen deprivation. This double mutant could be complemented by wild-type copies of sigD or sigE, indicating some degree of functional redundancy that can partially mask phenotypes of single gene mutants. However, the sigE gene was required for lysogenic development of the temperate cyanophage A-4L. Several other combinations of double mutations, especially sigE sigF, caused a transient defect in establishing diazotrophic growth, manifested as a strong and prolonged bleaching response to nitrogen deprivation. We found no evidence for developmental regulation of the sigma factor genes. luxAB reporter fusions with sigD, sigE, and sigF all showed slightly reduced expression after induction of heterocyst development by nitrogen stepdown. Phylogenetic analysis of cyanobacterial group 2 sigma factor sequences revealed that they fall into several subgroups. Three morphologically and physiologically distant strains, Anabaena sp. strain PCC 7120, Synechococcus sp. strain PCC 7002, and Synechocystis sp. strain PCC 6803 each contain representatives of four subgroups. Unlike unicellular strains, Anabaena sp. strain PCC 7120 has three additional group 2 sigma factors that cluster in subgroup 2.5b, which is perhaps specific for filamentous or heterocystous cyanobacteria.
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Project description:Although regulation of sigma factors has been intensively investigated, anti-sigma factors have not been identified in oxygenic photosynthetic organisms. A previous study suggested that the sigma factor, SigE, of the cyanobacterium Synechocystis sp. PCC 6803, a positive regulator of sugar catabolism, is posttranslationally activated by light-to-dark transition. In the present study, we found that the H subunit of Mg-chelatase ChlH interacts with sigma factor SigE by yeast two-hybrid screening, and immunoprecipitation analysis revealed that ChlH associates with SigE in a light-dependent manner in vivo. We also found that Mg(2+) promotes the interaction of SigE and ChlH and determines their localization in vitro. In vitro transcription analysis demonstrated that ChlH inhibits the transcription activity of SigE. Based on these results, we propose a model in which ChlH functions as an anti-sigma factor, transducing light signals to SigE in a process mediated by Mg(2+).
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Project description:Mycobacterium tuberculosis (Mtb) is well adapted to survive in macrophages and usually subverts the bactericidal mechanisms of these professional phagocytes. The adaptation of Mtb to the intracellular life depends on its ability to regulate the expression of its genes. Among the most important bacterial transcription activators are the sigma factors that bind to the RNA polymerase and give it promotor specificity. Sigma factor E (SigE) controls the expression of genes that are essential for Mtb virulence. Analysis of the macrophage transcriptional response indicated that proteins encoded by the sigE regulon are involved in the modulation of the macrophage inflammatory response. We compared the global gene expression of THP1 macrophages infected with H37Rv and SigE to the gene expression profile of uninfected macrophages.
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